All this time I was sauntering idly up-town, and as I did so I fell in with a stream of people coming from the Roman Catholic Cathedral. Walking among them, I noticed a woman coming rapidly towards me, who smiled at me encouragingly, even from quite a distance. Her face seemed strangely familiar, although I was unable to place her. Where had I seen those flashing black eyes before? Ah! I had it,--Mme. Argot. She was alone, and as she came nearer I saw she not only recognised me, but that she was intending to stop and speak to me. I was considerably surprised, but slowed down also, and we were just opposite to each other when her husband suddenly stepped to her side. A moment before I could have sworn he was not in sight. It was quite uncanny. His wife started and glanced fearfully at him, then tossing her head defiantly she swept past me with a beaming bow. He took off his hat most respectfully, and his long sallow face remained as expressionless as a mask. But I was sure that his piercing black eyes looked at me with secret hostility. The whole incident only occupied a minute, but it left a deep impression upon me, and started me off on an entirely new train of thought. What had the detective said? The guilty person must have been able to procure, for some time, however short, the key to the vacant apartment. We only knew of three people who were in a position to have done this. Miss Derwent, the French butler--well, why not the French butler? Those eyes looked capable of anything. I was sure that his wife was afraid of him, for I was certain that she had meant to stop and speak to me, and had been prevented from doing so by his sudden appearance. But what could she have wished to say to me? And why that gleam of hatred in her husband's eye? I felt myself so innocent towards them both. In fact, I had not even thought of them since the eventful Thursday, and might easily have passed her by unnoticed if she had not been so eager to attract my attention. Well, it would be queer if I had tumbled on the solution of the Rosemere mystery!