“Now listen, Mason, this man whom you saw in the carriage talking to your mistress at the Gare de Lyon, how do you know it was not your master?”
“The master, sir? Oh, I don’t think it could have been.”
“But you are not sure,” Poirot persisted.
“Well—I never thought of it, sir.”
Mason was clearly upset at the idea.
“You have heard that your master was also on the train. What more natural than that it should be he who came along the corridor?”
“But the gentleman who was talking to the mistress must have come from outside, sir. He was dressed for the street. In an overcoat and soft hat.”
“Just so, Mademoiselle, but reflect a minute. The train has just arrived at the Gare de Lyon. Many of the passengers promenade themselves upon the quay. Your mistress was about to do so, and for that purpose had doubtless put on her fur coat, eh?”
“Yes, sir,” agreed Mason.
“Your master, then, does the same. The train is heated, but outside in the station it is cold. He puts on his overcoat and his hat and he walks along beside the train, and looking up at the lighted windows he suddenly sees Madame Kettering. Until then he has had no idea that she was on the train. Naturally, he mounts the carriage and goes to her compartment. She gives an exclamation of surprise at seeing him and quickly shuts the door between the two compartments since it is possible that their conversation may be of a private nature.”