“Yes, a woman,” said Poirot, nodding his head. “You may not remember, Monsieur Van Aldin, but Miss Grey in her evidence mentioned that a youth in a cap and overcoat descended on to the platform ostensibly to stretch his legs. Me, I think that that youth was most probably a woman.”

“But who was she?”

Van Aldin’s face expressed incredulity, but Poirot replied seriously and categorically:

“Her name⁠—or the name under which she was known, for many years⁠—is Kitty Kidd, but you, Monsieur Van Aldin, knew her by another name⁠— that of Ada Mason .”

Knighton sprang to his feet.

“What?” he cried.

Poirot swung round to him.