Stuart's agitation grew more marked and it was only by dint of a palpable effort that he forced himself to resume.
"On the evening of the following day a lady called professionally. She was young, pretty, and dressed with extraordinary elegance. My housekeeper admitted her, as I was out at the time but momentarily expected. She awaited my return here, in this room. She came again two days later. The name she gave was an odd one: Mademoiselle Dorian. There is her card,"—Stuart opened a drawer and laid a visiting-card before Dunbar—"no initials and no address. She travelled in a large and handsome car. That is to say, according to my housekeeper's account it is a large and handsome car. I personally, have had but an imperfect glimpse of it. It does not await her in front of the house, for some reason, but just around the corner in the side turning. Beyond wondering why Mademoiselle Dorian had selected me as her medical advisor I had detected nothing suspicious in her behaviour up to the time of which I am about to speak.
"Last night there was a singular development, and to-night matters came to a head."
Thereupon Stuart related as briefly as possible the mysterious episode of the cowled man, and finally gave an account of the last visit of Mlle. Dorian. Inspector Dunbar did not interrupt him, but listened attentively to the singular story.
"And there," concluded Stuart, "on the blotting-pad, lies the sealed envelope!"
Dunbar took it up eagerly. A small hole had been burned in one end of the envelope and much of the surrounding paper was charred. The wax with which Stuart had sealed it had lain uppermost, and although it had been partly melted, the mark of his signet-ring was still discernible upon it. Dunbar stood staring at it.
"In the circumstances, Inspector, I think you would be justified in opening both envelopes," said Stuart.
"I am inclined to agree. But let me just be clear on one or two points." He took out the bulging note-book and also a fountain-pen with which he prepared to make entries. "About this cabman, now. You didn't by any chance note the number of his cab?"
"I did not."
"What build of man was he?"