“As I told you, sir, I never saw the gentleman’s face. That is what makes it so difficult.”

Poirot beamed and nodded.

“Precisely, exactly. I comprehend well the difficulty. Now, Mademoiselle, you have been in the service of Madame Kettering two months, you say. During that time, how often did you see your master?”

Mason reflected a minute or two, and then said:

“Only twice, sir.”

“And was that near to, or far away?”

“Well once, sir, he came to Curzon Street. I was upstairs, and I looked over the banisters and saw him in the hall below. I was a bit curious like, you understand, knowing the way things⁠—er⁠—were.” Mason finished up with her discreet cough.

“And the other time?”