search of Mark, I stepped into the office. My hand was in my side-pocket, and in my hand was the revolver.
"He began at once in his character of Robert—some rigmarole about working his passage over from Australia; a little private performance for my edification. Then in his natural voice, gloating over his well-planned retaliation on Miss Norris, he burst out, 'It's my turn now. You wait.' It was this which Elsie heard. She had no business to be there and she might have ruined everything, but as it turned out it was the luckiest thing which could have happened. For it was the one piece of evidence which I wanted; evidence, other than my own, that Mark and Robert were in the room together.
"I said nothing. I was not going to take the risk of being heard to speak in that room. I just smiled at the poor little fool, and took out my revolver, and shot him. Then I went back into the library and waited—just as I said in my evidence.
"Can you imagine, Mr. Gillingham, the shock which your sudden appearance gave me? Can you imagine the feelings of a 'murderer' who has (as he thinks) planned for every possibility, and is then confronted suddenly with an utterly new problem? What difference would your coming make? I didn't know. Perhaps none; perhaps all. And I had forgotten to open the window!
"I don't know whether you will think my plan for killing Mark a clever one. Perhaps not. But
