Van Aldin did not answer, but he was not satisfied. The conductor was told that he need not make up the beds. Any surprise he might have felt was obliterated by the largeness of the tip which Van Aldin handed to him. The three men sat in silence. Poirot fidgeted and seemed restless. Presently he turned to the secretary.

“Major Knighton, is the door of your compartment bolted? The door into the corridor, I mean.”

“Yes; I bolted it myself just now.”

“Are you sure?” said Poirot.

“I will go and make sure, if you like,” said Knighton, smiling.

“No, no, do not derange yourself. I will see for myself.”

He passed through the connecting door and returned in a second or two, nodding his head.