"My name is Mr. Roger Merton," I explained. "I have taken the liberty of calling upon you."

"Come into my study, Mr. Merton," said Dr. Rendall.

He spoke in a friendly enough voice, but if there was not a trace of suspicion in his eye too, I am greatly mistaken. And in both cases it seemed to me that it was suspicion tinged with apprehension, rather than the suspicion I was so deliberately cultivating. Indeed, I had not intended to cultivate any suspicion at all in this house, but fortunately (I think) I simply acted automatically.

Taking him altogether, Dr. Rendall was a decidedly more prepossessing looking man than O'Brien. In fact he was rather good-looking, with grey hair and moustache, face of a deep bronze-red hue and very blue eyes. He was well set up, and quite well dressed too in rough tweeds, and the only thing against him was that look in his eye as we exchanged our first sentences.

My wits were very wide awake by this time; I carried a picture of the outside of the house distinctly in my head as we turned out of the hall, and when we entered the study I knew it for the room where the blind had shut down.

"Is Mrs. Rendall at home?" I enquired.

O'Brien laughed.

"There are no ladies in this house, but just the doctor and me!" said he.

So no modest matron or maid had pulled the blind down. It had been Dr. Rendall's study blind, whipped down obviously by the doctor himself the instant he heard a strange footstep, and now raised again. Why had it been dropped? What had it hidden? In the look of the room itself there was not a suggestion of an answer to either question. It was just an ordinary man's study, a cross between a smoking room and a library, a much more comfortable room than the outside of that house promised. Yet people do not suddenly pull down blinds in the middle of the forenoon for no reason at all.

For a moment I thought of a passage at arms with a pretty housemaid as a solution. But it would obviously have been much quicker and simpler for any other party to flee the room than to make for the window and lower the blind. No; something had to be done which took a few minutes to do. I thought instantly of one possibility—the folding up or putting away of maps or plans. No doubt there were several other possibilities, but there seemed the best of reasons for not giving these worthy gentlemen my confidence. In fact quite a different course of action suggested itself.