The D Line

BY

L. T. MEADE & ROBERT EUSTACE

EORGE VAUGHAN hated all women except his old mother, who lived with him, and to whom he was devotedly attached. He was a little, thin, wizened man of about thirty-five years of age, looking, however, at least ten years older. He had keen, deeply sunk, dark eyes, a sallow face, a somewhat bald forehead, and beautiful slender hands as refined and white as a girl's. Vaughan from his earliest years had a crank, and that crank finally landed him in the profession by which he made his name. He had mechanical talent to such an extent that it almost rose to genius. At the age of five-and-twenty he gave up all other pursuits for the pleasure of clockmaking, and by the time this story opens he had acquired such immense skill in the mathematical part of the work that he became a consultant to the trade.

He occupied a small house in Bloomsbury, the lower part of which was devoted to his workshops and laboratories, and called himself by the rather high-sounding name of "Consulting Horologist." He and his mother lived in the rooms over his workshops. They kept no servant, the old woman being pleased and proud to perform all sorts of domestic duties for her son. He, on his part, although attached to her, was scarcely conscious of her presence, every interest being absorbed in the trade to which he devoted his life. As the days wore on, he made more and more wonderful clocks, and his advice was sought in difficulties by West End and City clock and watch makers; and by and by so widely did the man's fame spread that he was asked to test and regulate the chronometers for the Admiralty and Merchant Service. In this way he fast became rich—not that he himself regarded money as of the slightest consequence. He had no domestic tastes, did not care how he lived, ate his food without knowing what was put before him, when he did talk talked of clocks alone, and did more theoretical and practical work in that one special department than any other man in London.

To Vaughan was due the application of clockwork to locks of safes and strong-rooms. The essential point of the new safes was the following. They consisted of a bolt or bolts so controlled by clockwork that to open them was practically impossible, except when the clock mechanism reached a certain point. If the clock were set for a given hour, even the holder of the key could not open it again before that hour. Vaughan's safes were therefore considered practically impregnable, and the man became renowned in his own line.

Having a great deal to do, he now employed a large staff of skilled workmen, superintending the important part of the work, which always passed through his own hands.

He was a shy man, and the ordinary woman was his horror; but when forced for any reason to mingle with his fellow men he was genial and sympathetic enough, and his old mother was wont to say of him that he had the tenderest heart in the world. Be that as it may, nothing could exceed the horror of George Vaughan when, on a certain murky morning in November, his senior assistant entered his workshop and told him that a lady had called to see him on important and urgent business.

"I never see ladies, and you know it, Thompson," was his reply. He looked up almost piteously into the face of his assistant as he spoke.

The man gave a slight laugh.

"The lady is young, sir," he replied, "and seems in great trouble. She begs of me to allow you to see her; she won't keep you a moment, she says."

"Trouble?" muttered Vaughan. "Did she say she was in trouble?"

"Yes," said the assistant; "and she seems in trouble, too, sir," he added.

"Women call themselves in trouble if they scratch their fingers," replied Vaughan, giving utterance to an audible sniff. "I won't have her up here," he said then; "I'll go downstairs to see her, if I must."

He had a private sitting-room on the ground floor. As he entered it now a girl who was standing near the door went up to him and offered him a visiting-card.

"This is my father's card, Mr. Vaughan," she said. "You remember doing work for Mr. Lawrence Gaubert, do you not?"

Vaughan took off his spectacles and gazed at her in some alarm. She was a pretty girl, tall and slight, with dark eyes and a vivacious face; but there was an absence of all self-consciousness about her, and this very fact caused the little horologist to view her with more favour. He rubbed his glasses and put them on again.

"Yes, Miss Gaubert," he said, "I know your father. Has he sent you with a message to me?"

"No, he has not," replied the girl. "I have come on my own account." She pushed up her veil as she spoke and looked Vaughan steadily in the face. "I have come on a private and urgent matter," she said, dropping her voice. "I can quite understand that you would rather not see me; nevertheless, my business is so special and important that that fact simply weighs for nothing. I must ask you to listen very attentively to what I have to say."

Vaughan stood near the table; he leant one of his slender white hands upon it now and looked the girl all over. He did not ask her to seat herself.

"You supplied my father with a time-lock for one of his safes about six months ago," she then said.

"I remember the transaction quite well," replied Vaughan; "but may I ask what your special business is?"

"I am coming to that. My father means, Mr. Vaughan, to call upon you to-day. He is coming here to make a special request of you. Now, I want you"—she coloured; then the colour left her face, she stepped up close to the unwilling man and said in a low tone—"I want you, Mr. Vaughan, to refuse to do what my father wishes. There is danger to you if you accede to his request, there is great danger also to him. I love my father, notwithstanding—notwithstanding" Her lips trembled, her voice dropped, then she raised it and said briskly, "I want you to make me a promise—I want you to refuse the request he is about to make you."

"You are very mysterious, Miss Gaubert."

"I am mysterious because I am obliged to be," replied the girl. "It would only make matters awkward for you if I told you more. This visit of mine is of a private nature, and I trust to your honour to reveal it to no one. I must repeat that there is grave danger to you if you do what my father means to ask you to do. I have come to you at personal risk to beg of you to refuse him."

"I am obliged to you," said Vaughan briskly, "but"

"Yes, what do you mean to do?" asked the girl.

"I can make you no promise."

She clasped her hands, the tears suddenly filled her eyes.

Vaughan had a perfect horror of women in tears. He nearly backed towards the door in his distress.

"I beg of you to leave me," he said. "I—I never receive ladies here."

"I will go the moment you make me your promise."

"I cannot, I really cannot. Young ladies know nothing whatever about business."

"I know what I am saying. I am not an ordinary girl. I live alone with my father, and, notwithstanding everything, I love him more than anyone else in the world. There is great danger to you if you do what he requests you to do, also great danger to him. If you refuse you are safe and he is safe. Can you not do what I ask you, and can you not keep my counsel?"

"I must be guided altogether by circumstances, Miss Gaubert; and now I beg of you to leave me."

A despairing look swept over Miss Gaubert's pretty face.

"A girl does not go out of her way," she repeated, "to see a man like you for nothing. Can you not understand that I am risking much by giving you this warning?"

"As I said before," answered Vaughan, "I am obliged to you, but my mind is made up. I can make no promise. The only thing I can say is that if Mr. Gaubert should call upon me I will remember that you have paid me this visit."

"At least you will not betray that I came here?"

"I will say nothing whatever about it."

"Then I can do no more. I had hoped that you would understand my sincere wish to serve you."

"Thank you," replied Vaughan stiffly. A moment later he was alone. He stamped his foot with impatience.

"Confound all women!" he said to himself. "My time wasted by a silly, hysterical girl. But what did she mean? If there is a safe and dependable man in the world it's Mr. Lawrence Gaubert. I made him one of my very best time-locks. I never saw anyone take a more intelligent interest in my special business."

Vaughan generally lunched at a neighbouring restaurant. He went out now, but as he ate his chop and drank his pint of bitter the face of Miss Gaubert, full of anxiety and pleading, rose up again and again before his mental vision. What did she mean? She was honest, at least, he said to himself. Oh, of course hysterical, hysterical like most women. He resolved to forget her and went back to his business.

An hour after lunch his assistant brought him a card.

"A gentleman to see you, sir," he said. Vaughan glanced at the card.

"By Jove!" he said to himself, "that girl was right!" He read the name—"Mr. Lawrence Gaubert." "Show Mr. Gaubert up," he said to his assistant.

A moment later a stout, middle-aged man, scrupulously but quietly dressed, entered the room. Vaughan was very civil to him. He begged his client to seat himself and inquired what he could do for him.

"I hope your time-lock is going well, Mr. Gaubert," was his first remark.

"Ah! then you remember all about me? That is capital!" answered Gaubert. "Well, Mr. Vaughan, the time-lock is not so satisfactory as I could have wished—in fact, it has got out of order. I have called to see you to-day on that very subject, for it turns out to be an important matter."

"I dare say I can soon rectify anything wrong in the lock," said Vaughan; but, in spite of himself and against what he considered his better judgment, he could not help remembering the mysterious visit of Gaubert's daughter. "I want you to help me in a very urgent matter," continued Gaubert. "I am in a most uncomfortable position, and in order to explain things fully I must take you into my confidence, a confidence which I know I can trust. You are perhaps aware that I am a banker and foreign exchange agent, and that my place of business is in Nicholas Lane. I bought two time-locks from you, one for my office, one for my own private house. Up to the present the one attached to the safe in my private house has gone splendidly. It was made from one of your best designs."

"One of my very best," said Vaughan, bowing his head.

"Well, now I want to ask you an important question with regard to it. Is there any chance of such clockwork getting out of order if not tampered with?" "Very little," was the horologist's answer.

"Then, that being the case, my position is most unpleasant. Until within the last twenty-four hours your time-lock has worked splendidly—the one which belongs to my own private safe. I time it to open exactly at nine o'clock in the morning—that is, every twenty-four hours. This morning I had an appointment of a very important nature with a distinguished client, to whom I was to hand some valuable property. To my dismay, the lock refused to open. It was most inconvenient. I apologised to him, but that did not make matters more comfortable for me. My client and I are going together, in connection with our business, to Birmingham this afternoon, meaning to return to-morrow evening; and at nine o'clock to-morrow night I have promised to have the safe open and to hand him some securities. It is absolutely necessary that he should have them then, as he is leaving England for Genoa by the midnight express. What I want to ask you now is this. Can you come down to my house with tools and open the safe for me to-morrow evening?"

Vaughan made a very slight pause before he answered. He thought of the pleading dark eyes of the girl who had begged of him so passionately to refuse this request.

"A silly, hysterical, unbusiness-like creature!" he muttered under his breath. Aloud he said after this very brief pause, "I will come, with pleasure, Mr. Gaubert."

Gaubert uttered a quick sigh. Was it of relief? He rose immediately.

"Thank you, Mr. Vaughan," he said. "I suppose there will be no difficulty in opening the safe? And after opening it you can close it again, I presume?"

"Easily," answered Vaughan; "and I shall doubtless at the same time be able to tell you what is wrong with it."

"You will be doing me a great service. I am firmly convinced that someone has been tampering with the safe; and now before I go I want to ask you one more question. Would it be possible for anyone to open such a lock and to close it again, provided he had the key, at a time for which it was not set, and yet to leave it in such a condition that would make it impossible for anyone to say it had been tampered with?"

"Only a very skilled workman could do that," replied Vaughan, in a thoughtful voice, "otherwise where would be the security of these safes?"

"I see," answered Gaubert. "Well, I am very much obliged to you, Mr. Vaughan. Of course I will pay you handsomely for the service you are about to render me. I am engaged just now on some very important transactions, and this accident has upset me not a little. One thing more—you will pardon this request, but may I ask you to come to my house alone? I will tell you why. The negotiations with my client are of a strictly private nature—no one but my chief clerk knows anything about it—it is in connection with the Italian Government; and I must even ask you to keep secret the identity of my client when you see him. This is the reason why I am conducting the business at my own house instead of at the office."

"I understand," answered Vaughan. Again the face of the girl with the dark eyes and imploring voice flashed before him. Again an angry protest rose in his heart at the silliness of all women. He said quietly, "I will accede to your wishes in all particulars."

Gaubert held out his hand. As Vaughan took it he said, "Is the mechanism of the clock still going?"

"Oh, yes, it is still ticking."

"Then I dare say there is not much wrong. Perhaps the train became a little slack, and the clock will miss a period and open all right at the end of the next twenty-four hours. However, I cannot tell you much until I see it."

"Thank you' answered Gaubert. "It is lucky for me to have your help in an emergency like the present."

He shook hands again with Vaughan and left him. The moment he did so Vaughan sat down to some mathematical problems. He became absorbed over his abstruse calculations, and had evidently forgotten Miss Gaubert's visit, and also that of Gaubert himself, when the door of his room was hastily flung open, and a man whom he knew very well to be one of the most able detectives of Scotland Yard entered. This man's name was Thomas Scott. Vaughan had made his acquaintance the previous year in connection with a theft on a bank vault fitted with his own design of clockwork locks, and since then he had often met Scott. A month ago Scott had been induced to buy a rather expensive and peculiarly constructed watch from Vaughan, and Vaughan's first thought was that he had come to see him about it.

"Has it stopped, or is it going all right?" he said, with the ghost of a smile.

"The watch? Oh, I have not come on that account," replied Scott. "I want to ask you a question, Vaughan. You are about the only man in London who can tell me."

"Well, what is it?" asked the horologist.

"I want to know something more about these clock-locks. You know you are responsible for them. Would it be possible for anyone to open a box with a key at a time not set, and could the lock afterwards be opened at its own special period without anybody detecting that it had been tampered with?"

An angry expression broke from Vaughan's lips. He sprang suddenly to his feet.

"Have all the burglars in London suddenly begun to break into safe deposits, or what?" he asked.

"What do you mean?"

"Only this. That the identical question you have now put to me was asked me by another man not half an hour ago."

"Was it, by Jove? Who was he?" asked Scott.

Vaughan was silent for a moment.

"I don't see why I should not tell you," he said; then in a careless tone, "he is one of my best customers—Mr. Gaubert."

"Oh, he's been here, has he?" said Scott. "I don't wonder, he's in a fine stew. He's been to see me this morning about it. He has got some thirty thousand pounds' worth of stones coming from Brazil to-morrow night. They are to be sent from Liverpool in a clock-lock box, and a special clerk is to bring them up. They are consigned to Gaubert as the agent, the box is timed to open at nine in the morning, and it will then go on to the millionaire who is the purchaser, a Mr. Harcourt. This morning Gaubert was put into a fine state of terror by a cable saying that Captain Halkitt, the great American bank thief, is after the jewels. He came to me shaking all over. I never saw a man in such a downright state of blue funk. I didn't think so much about the matter myself. The box is carefully guarded, and the clerk who brings it from Liverpool is above suspicion. Gaubert, with one of our detectives, will meet the train to-morrow night and take the box containing the treasure to his private house, as his office is shut up at so late an hour. Now, the question I want to ask you is this. Do you think that the box could be opened and shut again without anyone knowing and spotting the fact that it was tampered with afterwards?"

"You ask me a queer question," replied Vaughan, "and I can only say in reply that it depends on the man. I do not believe there are three men in London who could do it, even if they had the tools and the time. It would require a very special knowledge of clock-locks to do it properly."

"But you, I suppose, could do it?"

"Well, of course I could, and it would be all right. By the way, I don't know if there is any harm in telling you that Mr. Gaubert has asked me to go to his house to-morrow night to open his ordinary deposit safe for him—the lock has gone wrong."

"Has it? " replied Scott. A thoughtful expression flitted across his face for a moment, and his deep-set eyes twinkled. "Now, this is strange," he continued. "Gaubert has told me about that business, too. I think he suspects one of his men, and we are keeping an eye on a rather suspicious clerk on the staff. What time are you going down?"

"At nine o'clock."

"Well, he will be back from Euston then with the stones, as the train gets in at 8.10. My own impression is that the man is in a state of panic. I suppose the matter of the safe going wrong this morning, coming on top of the cable that Halkitt is after the stones, has made him extra anxious. Of course, Captain Halkitt is a prince in the profession, and I must say I would do a great deal to lay my hands on him. He is about the cutest man in the two continents. Well, I must be off. I have got my hands full, I can tell you."

"All right," said Vaughan; "you may rest assured that the time-lock cannot be tampered with without discovery. I am the only man in London who could do that." He laughed as he spoke.

Scott left him and he went down to his workshop. Vaughan was now busy perfecting a new discovery which would even put the clock-locks in the shade. He was busy over it, and had eyes, ears, and thoughts for nothing else during the remainder of the day.

On the following morning he was rushing downstairs in a great hurry, when, to his infinite disgust, he saw the pretty girl who had visited him the day before coming up. She paused when she saw him and held out her hand.

"How do you do, Mr. Vaughan?" she said.

"How do you do, Miss Gaubert?" he replied. "I—I happen to be particularly busy. If you will excuse me, I will wish you good morning."

"I cannot excuse you, Mr. Vaughan," answered Miss Gaubert, in a firm voice. "If you are busy and are going out, I can walk with you as far as the place you are going to."

"But, excuse me, I never walk with ladies," said Vaughan, turning first red and then white.

The girl partly raised her brows and an amused smile flitted across her face.

"I won't do you any harm," she said; "but I must speak to you. It will take up less of your time if I walk down the street with you. I have got something I must and will say."

Vaughan shrugged his shoulders. He could not well push the girl aside and rush past her. Although he hated women, for the sake of his mother he could not be absolutely rude to any of them. He buttoned his rather shabby frock-coat tightly down his slender little person, and, saying in a voice the reverse of flattering, "If you must come, I suppose you must," ran in front of the girl and opened the hall-door for her. The moment they got into the street Vaughan walked at a rapid pace, but the girl's steps were quite as quick as his.

"You cannot shake me off," she said. "May I ask you if my father called to see you yesterday?"

"Yes," replied Vaughan, "you were right with regard to that matter."

"Of course I was right," said the girl. "My name is Hilda Gaubert, and I am my father's only daughter. I love him as much as your daughter, Mr. Vaughan, would love you if you happened to be married and to have one."

"But I am not married," replied Vaughan. "Heaven forbid! Matrimony is the last thing I think of." He turned a fierce red. His inclination was to dash past the girl and rush up the first side-street he could find.

"Now, miss," he said, restraining this impulse with a great effort, "may I ask what you do want with me?"

Miss Gaubert turned and faced him.

"You know quite well what I want," she said. "You refused to do what I wished yesterday. My father came to you with a request—you acceded to that request, did you not?"

"Certainly I did. I am not to be influenced by hysterical girls."

Miss Gaubert took no notice of this rude remark.

"Even now there is time for you to change your mind," she said.

"But I don't intend to change it, miss. I mean to see your father this evening."

"At his own house? He has asked you to open a safe for him; one of his time-locks has gone wrong, and he has asked you to open the safe?"

"I decline to discuss the nature of the business which takes me to your father's house."

"Very well; I cannot press for your confidence, but I can and will repeat that there is grave danger to you if you go. You will repent it, Mr. Vaughan, and you cannot say when the time comes that Hilda Gaubert did not warn you."

"No, I cannot say that," replied the little man. He paused as he spoke. "I am about to go in here," he said, pointing to an archway—"no fit place for a young girl. I will wish you good morning, miss."

To his surprise and almost terror the girl seized him by the arm.

"Don't be obstinate," she said, and there were tears in her pretty eyes. "I ask you for your own sake, and for the sake of my father, to stay at home this evening."

"I am really sorry for you, miss; you are a very strange young lady, but it is impossible for me to do what you wish."

"In that case I ought to tell you more, and yet I dare not. It is very hard on me that you will not understand, but"

"I am in a great hurry, Miss Gaubert."

As Vaughan spoke he removed the girl's hand, which still rested on his arm, and stepped back with a gesture almost of repugnance. Her beautiful brown eyes flashed at his action.

"You misunderstand me and I can do no more," she said. She turned and walked up the street.

Vaughan could not help gazing after her. As be did so he felt almost foolish.

"She was a pretty lass, and I suppose I hurt her that time," he said to himself; "hurt her feelings, that is. What a queer lot women are—all nerves, quite jerky with 'em! I wish I could make a clock as full of nerves as a woman; but there! it might give me as much trouble as most men find with their wives. I married? I'd like to see myself in such a predicament!"

Having completed his business he returned to his workshop. Nothing special occurred until three o'clock in the afternoon, when his telephone bell rang. Grumbling at the interruption, for he was just at the crucial point of his next great discovery, Vaughan went to answer it. To his surprise the superintendent of the Old Jewry City Police spoke to him.

"Come round as soon as possible. Mr. Scott wants to see you on a most important matter."

Vaughan replied that he would go to the Old Jewry within half an hour. He turned to continue his own business, a frown between his brows. He disliked Scott's criminal cases, and did not wish to be dragged into any of them.

"They take up my time, and, whatever I am, I am not a detective," he muttered. "My discovery is near completion, and I am called away to attend to matters which are no concern of mine."

When, therefore, he reached the head City police-station he was by no means in a good temper. He was shown at once into a private room, where Scott and the superintendent were waiting for him. The two men looked uncommonly serious.

"Well, what is it now?" asked Vaughan, just nodding to the superintendent and shaking hands with Scott. "I am particularly busy. I wish you men would clearly understand that I don't care twopence how many thieves you take up in the course of the day, nor how many villainies you expose. I want to attend to my own special work."

"Oh, sit down," said the superintendent. "Be assured we would not disturb you if we could help it; but the matter is all important, not only to us, but also to you. Now please listen. Scott and I have something of importance to tell you, but before we say a word further we must pledge you to secrecy over the communication."

Vaughan nodded his head.

"I never betray confidences," he said. "All I beg of you is to hurry."

"I will be as quick as I can, Mr. Vaughan," said Montagu, "only please give me your careful attention. I dare say you will hardly believe what I am about to tell you. Indeed, I can hardly realise it myself, for, if the suspicion which Scott and I have formed turns out to be true, a monstrous scheme to commit a big crime is on foot. More than this, our position as the official force is in a most strange condition, because without your assistance, Mr. Vaughan, our hands are practically tied."

The look of annoyance had now smoothed away from Vaughan's forehead, he was listening with attention.

"Is it true that you are going to Mr. Gaubert's house at nine o'clock this evening?" continued Montagu.

"Yes, I mentioned the matter to Scott yesterday."

"Will you answer the rest of my questions? You are going there to open Gaubert's safe because the time-lock has gone wrong?"

"That is the case."

Montagu now drew his chair forward, bent towards Vaughan, and lowered his voice.

"I have reason to suspect," he said, "that the box you will have to open is not the safe which contains his ordinary papers, but the box containing the stones from Brazil. There is, I believe, a colossal plot on foot to steal these stones."

"Good Heavens!" cried Vaughan, "you don't mean to say you suspect Gaubert? He is about one of the best and most honest fellows I ever met."

"So you think. But it is within the bounds of possibility that he is the reverse of what you consider him. I may be quite wrong, of course, but in view of my suspicion being correct, I must leave no loop-holes by which the criminals can escape. Granted the suspicion I hold to be right, my interpretation of the whole scheme is this. Gaubert and his accomplices get you to his house because you are practically the only man in London who can help them to open the box which has a time-lock, and which contains the stones, without at the same time injuring the lock. When you have opened the box for them, and they have removed the gems, they will compel you to close the box again, and to set the clock as if it had not been touched. If you refuse, an unpleasant alternative will be presented to you. They will then send the box without the stones to Harcourt, to his country house. He will receive the box from Gaubert without the slightest suspicion, and won't discover the theft till nine o'clock to-morrow morning, when he opens it with his own key at the time set. The thieves thus utilise the very mechanism designed to prevent robbery to their own advantage, because it gives them a clear eleven hours to cover their tracks."

Vaughan was a man who never yielded to emotions of any sort, but he was startled now, his confidence in Gaubert slightly shaken, and an uncomfortable feeling with regard to Gaubert's daughter began to assail him. In his opinion Gaubert was as honest and straight a fellow as ever breathed, but why had Miss Gaubert come twice to see him? The alarm in her face was surely genuine. How earnestly she had implored him not to accede to Gaubert's wishes. Pooh! she was nothing but a silly, romantic girl. Nevertheless, at that moment, Vaughan could not help coming to the conclusion that Miss Gaubert, young and childish and silly as she was, had very much the same ideas as the superintendent of police. He could not and would not betray her, but the memory of her words and her actions gave him an uneasy sensation. After a short silence he said quickly—

"If I find that this incredible plot which you suggest is true, my course will be clear. I shall refuse to close the box again, and thus give the alarm."

"And pray, if you did, where would your evidence be that they were going to steal the gems?" answered Montagu. "You must remember that Gaubert, as Harcourt's agent, has a right to their possession. The other men present would of course be his tools. They would deny every word you said, and you would look a fool, if not worse. It would be only necessary for Gaubert to say that he had asked you to open the box in order that he might see if the stones were safe. Yes, even if you could give the alarm, you would do no good, and Gaubert and his accomplices would take precious good care that you were not allowed your liberty."

"Then what do you propose to do?" asked Vaughan. "Remember, I don't for a single moment believe in your suspicion; but, supposing it to be true, what can I do? Had I better keep out of the whole thing?"

"There is our difficulty," answered Montagu. "We want you to go on with it, in order to prove whether our suspicions are right or not. At present we cannot arrest Gaubert because we have no evidence against him. If we manage this matter well, you may be the means of giving us the necessary evidence, and we may also arrest Captain Halkitt, the well-known professional thief. Gaubert, perhaps to blind us, has already taken us partly into his confidence, and has asked us to send detectives with him to meet the train by which the stones arrive to-night from Liverpool. Our detectives go with Gaubert to the station to meet the clerk who brings the stones and will conduct them all to Gaubert's house. After that our part to all appearance ends."

As Montagu spoke he began to pace the floor restlessly.

"There never has been such a situation in all my experience," he muttered. His heavy brows were drawn down over his deep-set eyes.

"I had better not go," said Vaughan, rising as he spoke; "my time is too valuable for me to allow myself to be mixed up in a burglary."

"And yet we want you to go," said Montagu. "It is most important that we should catch Captain Halkitt, and my impression is that he will be with Gaubert to-night. By your aid we will catch that well-known scoundrel, and also Gaubert. Without it, I confess, we can do nothing."

"If your suspicions are true," said Vaughan, "you had better remain outside with your men, and I will give you a prearranged signal."

"And how will you do that?" said Scott. "Do you suppose those men are fools? They will take precious good care you cannot. Besides, we don't want you to signal unless the stones have been removed from the box, and not put back again, for our wish is to catch the thieves red-handed. Whatever signal you give must be something that we can detect, and that they won't notice, however closely they watch you."

"Well, that settles the matter, for it is impossible," said Vaughan decisively.

"By Jove! but it must be made possible," said Scott. "We have got to solve that puzzle. Something must be done which they won't notice and which we will, something which we will observe even if the blinds are down. Sight won't do it. Sound won't do it—why, it's maddening!"

Scott began to pace the room in deep thought, and even Vaughan saw plainly the extraordinary position that he and the two detectives were in. Of the problem to which they were now brought face to face he could certainly see no possible solution. From the very nature of things, what could he do in a closed room which would give warning to someone outside the house, and yet not be noticed by those in the room, who were evidently on the alert to prevent the very occurrence of such a thing?

"It all hangs on our finding a solution to that one point," said Montagu. "We must discover a signal which you can give, and which they won't notice, and which we will see. We have got to think it out. Now listen, Vaughan. If Scott and I between us can think of something between now and eight-thirty, we will communicate with you. If you don't hear from us, don't go at all."

"But," said Vaughan, "what excuse shall I give Gaubert, for, after all, your suspicions may be wrong? I have promised to go, and if he is an honest man I don't want to fail him."

"We will make it all right for you," said Montagu. "You must aid us in this matter now. If we cannot think of the proper signal you are better away than there. If we do think of a signal we will let you know between now and eight-thirty. Please be ready, and don't leave your house unless you hear from us. This is a matter of life and death."

"Life and death?" echoed Vaughan. Once more he thought of the girl. He had been rude to her. Was she right, after all? She was anxious enough and earnest enough in all conscience. She had warned him of danger, she had implored him not to accede to her father's request.

"You had better leave us now," said Montagu. "If you follow our instructions you, at least, are safe, and the time is getting short."

Vaughan went. He felt unduly, unnaturally excited, and during the rest of the afternoon his mind was so full of strange surmises that he did not attend to his ordinary work with his customary skill.

At eight o'clock he went to his workshop, collected the tools he might possibly want, and put them in a bag. He had just got everything ready when he heard his telephone bell ring sharply. He ran into his private office—Montagu's voice replied to his.

"Do you want any soldering tools for your work?" asked Montagu.

"No," answered Vaughan.

"Listen carefully, then. Take spirit-lamp and solder. If our suspicions are right, and you are asked not to open the safe, but the box which contains the stones from Brazil, say that you must detach something which you can weld again; then if they take out the gems and do not put them hack in the box, and ask you to close box without gems, prepare solder, use plenty of common salt with your flux; but if gems are put back in box, when you close it again do not solder at all. See? Repeat back to me what you hear."

Vaughan did so.

"All right. Will explain later. You are quite safe. Now go. Good-bye."

Vaughan scarcely waited to consider the strange request made of him, but hurried back to his workshop. He prepared a flux with a large quantity of chloride of sodium, put a spirit-lamp and soldering tools into his bag, then hailed a hansom and gave the driver Gaubert's address. As he stepped into the hansom he fancied he saw a man watching him from the opposite side of the street, but when he looked again through the window the man had vanished.

At three minutes to nine he drew up at Airdale Terrace. Gaubert's house was No. 8. As he rang, stoical, matter-of-fact little man that he was, he felt his heart beating quickly. The door was opened almost immediately by Gaubert himself. He conducted Vaughan into a dimly lit hall.

"So good of you to come, Mr. Vaughan. You are the very man I want. Will you come in here?"

As Gaubert spoke he opened a door and Vaughan found himself in a small room with a single incandescent light hanging from the ceiling. Two other men were present—one of these Gaubert introduced to Vaughan as his chief clerk, and the other as Signor Fratelli, his client. Signor Fratelli stood rather in the shade. He was a tall, thin man, with a heavy moustache and beard.

"Now," said Gaubert, "here is the tiresome box. Will you kindly open it with as little delay as possible, as Signor Fratelli is anxious to be off."

Vaughan looked at the box.

"I thought you told me that I was to open your safe?" he said abruptly. He looked full into Gaubert's face as he spoke.

"The safe is all right. This is the matter we want attended to," said Gaubert, speaking quickly, a frown between his brows. "It contains one of your time-locks. I purchased it, not from you, but from " he mentioned a well-known firm in Piccadilly.

Just at that instant, and before Vaughan had begun to set to work on the box, the door of the room was flung open and the dark-eyed girl ran in. She ran up to Gaubert and laid her hand on his arm.

Before she could say a word Gaubert interrupted in a voice of keen annoyance, "Go away, Hilda—we are busy."

"I must speak to Mr. Vaughan," she answered. "Mr. Vaughan, you are not to do what my father wants."

"Leave us, Hilda; don't be silly," said Gaubert. He took her arm as he spoke and tried to drag her from the room. She uttered a cry, wrested herself away from him, and the next moment had fallen on her knees.

"Don't, father," she cried; a heavy sob came from her throat. "Listen, Mr. Vaughan," she continued, turning to the horologist. "I have come to you twice. I have twice implored of you not to help my father in this matter. Father, you shan't commit this crime. I am here to prevent it. I am not afraid. Mr. Vaughan, you are asked to help these men—my father and these men, to commit a very great" But before the words had left her lips, to Vaughan's horror, Gaubert had struck the girl sharply on her forehead. She uttered a cry and fell back half stunned.

"Take her away at once, Pryce," said Gaubert, turning to his chief clerk; "take her upstairs. Gag her, and lock the door of the room. Come back immediately afterwards."

Vaughan turned to Gaubert.

"I do not care for women," he said; "but when a man strikes a woman, and that woman happens to be his daughter, I—sir, excuse me, I would rather not undertake this job."

"And you will do it, if you please, Mr. Vaughan, and as quickly as possible," said Gaubert. His whole face had altered. "It is a matter of life and death," he continued. "Life to you if you do it, death if you decline. We have a loaded revolver in this room. If necessary we shall use it. Now you know the worst."

Vaughan stood quite still. He had never known fear in his life, and he scarcely experienced it now. Nevertheless, he knew that he was alone in the room with three desperate men.

"Open that box and be quick about it," said Gaubert.

"Suppose I refuse?" answered the horologist.

"Then, sir, you will never leave this place alive."

Vaughan stood quite still considering, his hand rested on the box. After a moment he said quietly—

"In that case I have no choice." He sat down by the table and began his work. His manner was quite calm and quiet, as if the terrible scene through which he had just lived had never been enacted. He worked for a moment or two, then looked up.

"I am obliged to break a fragment of the brass-work," he said; "but I can easily make it good with a little solder afterwards."

"Very well, go on," said Gaubert; "anything to get the matter through."

The man who had carried the girl away had now returned to the room. As he did so he turned the key in the door. The three men clustered round the horologist, watching him intently.

Vaughan continued his delicate work. His fingers did not shake. Had they done so he might have spoilt the minute mechanism with which he had to deal. At the end of a quarter of an hour he had opened the dial, adjusted the mechanism, and was ready to put the key in the lock. Gaubert immediately handed him the key. He fitted it, unlocked the box, and lifted the lid. Inside lay a large leather-covered box. The moment it appeared the man who called himself Signor Fratelli stepped forward, lifted it out and opened it. Inside was a mass of glittering jewels. With a rapid movement the Italian transferred all the jewels to his own pocket. The leather-covered box, now quite empty, was put back into the safe.

"If Mr. Vaughan will kindly close the box, and set it to open at nine to-morrow morning, we shall be obliged," said Gaubert.

"Very well, I have no choice," answered Vaughan. He knelt down and started to work. Opening his bag he got out his spirit-lamp and blowpipe, and, using the flux he had prepared, lit the lamp and played the flame upon it. The men watched him eagerly, standing motionless over him. In a few moments he had finished, and the box was shut once more.

"That is good! " exclaimed Gaubert. "You are certain that the box cannot be opened till nine o'clock to-morrow morning?"

"Quite," answered Vaughan. "I can go now, I presume?" He had scarcely said the words when at a preconceived signal he found himself flung back. Before he could struggle, utter a word, or make the faintest show of resistance, a towel was tightly drawn round his mouth and nostrils, his hands were handcuffed, and his legs bound with cords. The light in the room was instantly extinguished, and the three men vanished into the passage outside.

Vaughan found himself lying on the floor in the darkness, unable to move or utter a sound. He heard the men hurry down the hall. They were escaping with their booty, and he was powerless to prevent it. He heard the hall-door open, and listened for the sound of its slamming to again, when instead a shout fell on his ears. Fierce, angry words followed, and then there was the sound of a desperate scuffle. The next instant, to his immense relief, Scott, followed by Montagu, dashed into the room. The men switched on the electric light.

"Well done!" cried Montagu excitedly, and releasing Vaughan in a moment. "This is about the smartest of all smart jobs."

The horologist struggled to his feet.

"Have you got the scoundrels?" he cried.

"Yes—safe and fast, thanks to you," cried Scott.

"Well, there is another victim," said Vaughan—"a girl. Find her—she is somewhere in this house—a pretty girl, and a brave one. She tried three times to save me, and twice out of those times I repulsed her—the last time I was powerless. They half murdered her between them. Find her immediately."

"Good Heavens!" exclaimed Scott, "is there worse behind? Come with me at once, Montagu, and you too, Vaughan."

They all left the room and began to search the house. In an attic at the top they found Hilda Gaubert. She was gagged and bound. When they released her she staggered half-fainting to her feet.

"Has my father gone? Have they murdered Mr. Vaughan?" she cried. "Oh, no, thank God! at least you are safe," she said, as her eyes fell upon Vaughan. He went up to her and took her hand.

"You are the bravest woman I ever met in all my life," he said, "and I behaved disgracefully to you. Will you forgive me? I will never say again that women are wanting in pluck."

"But has my father done it?" cried the girl. "Has he stolen the stones?"

"Alas, Miss Grubert, I have no good news for you," said Scott. "We suspected your father, and took steps to prevent his carrying out his design. We have been obliged to arrest him. He and that prince of scoundrels, Captain Halkitt, are even now being taken to the police-station."

The poor girl fell back against the bed on which she had been bound, her face was white as death.

"You must come home with me. My old mother shall look after you. You are the pluckiest girl I ever met," said Vaughan. But then he added, turning to Montagu, "What did you mean by that extraordinary signal? Why did you put me on that soldering job?"

"I will tell you," said Scott. "It was about the sharpest thing we ever thought of."

"But how could you see it in a room with the blinds down? Where were you?"

"Listen. Montagu and I were in a room in a house about a hundred yards off. Now I will let you into our secret, only you must keep it to yourself, for the stress and strain of this matter has developed our brains, and we have made a most valuable discovery in the field of detection. You know what a spectroscope is?"

"Of course," answered Vaughan.

"Well, you understand that by means of the spectroscope light is split up into red, orange, yellow, green, blue, indigo, violet—that is, the rainbow. Anyone looking through a spectroscope at a light in which sodium was burned would see a bright yellow perpendicular line in the D position. You put so much sodium into your flux that the line started out extremely clear, though it could only be seen through a spectroscope. We had a spectro-telescope focussed on the slit of light above the blind in the room where you were, thus giving a perfect spectrum of the light in the room. Directly, therefore, you used your blow-pipe the D line from the salt shot up as clear as possible. Now, what do you think of that for a signal? They would never have dreamed of such a thing."

"You certainly deserve your position as head of the Criminal Investigation Department," cried Vaughan. "It is the smartest idea I have ever heard of." "Well, keep it dark," said Scott, "for we shall use it again as occasion warrants. Now, Miss Gaubert," he said, turning to the girl, "will you stay here or will you go back with Mr. Vaughan?" "Yes, come with me," said Vaughan. "You must not be left alone. I owe you reparation for the cruel way I treated you," he added.

"If only you had believed in me, this great crime could not have been committed," was her faint reply. "But," she continued, looking into his face, "I will go with you."