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 Van Aldin's face expressed incredulity, but Poirot replied seriously and categorically.

"Her nameor the name under which she was known, for many yearsis Kitty Kidd, but you, Monsieur Van Aldin, knew her by another namethat of Ada Mason."

Knighton sprang to his feet.

"What?" he cried.

Poirot swung round to him.

"Ah!before I forget it." He whipped something from a pocket and held it out.

"Permit me to offer you a cigaretteout of your own cigarette-case. It was careless of you to drop it when you boarded the train on the ceinture at Paris."

Knighton stood staring at him as though stupefied. Then he made a movement, but Poirot flung up his hand in a warning gesture.

"No, don’t move," he said in a silky voice; "the door into the next compartment is open, and you are being covered from there this minute. I unbolted the door into the corridor when we left Paris, and our friends the police were told to take their places there. As I expect you know, the French police want you rather urgently. Major Knightonor shall we sayMonsieur le Marquis?"