Poirot shrugged his shoulders.
"It is quite simple," he said; "some one stepped in ahead of the Comte."
There was a long pause.
Van Aldin seemed to be turning things over in his mind. When he spoke it was without beating about the bush.
"How long have you suspected my son-in-law, M. Poirot?"
"From the very first. He had the motive and the opportunity. Every one took for granted that the man in Madame's compartment in Paris was the Comte de la Roche. I thought so, too. Then you happened to mention that you had once mistaken the Comte for your son-in-law. That told me that they were of the same height and build, and alike in colouring. It put some curious ideas in my head. The maid had only been with your daughter a short time. It was unlikely that she would know Mr. Kettering well by sight, since he had not been living in Curzon Street; also the man was careful to keep his face turned away."
"You believe he—murdered her," said Van Aldin hoarsely.
Poirot raised a hand quickly.
"No, no, I did not say that—but it is a possibility—a very strong possibility. He was in a tight corner, a very tight corner, threatened with ruin. This was the one way out."
"But why take the jewels?"