Holmes was for the moment as startled as I. His hand closed like a vice upon my wrist in his agitation. Then he broke into a low laugh and put his lips to my ear.

"It is a nice household," he murmured. "That is the baboon."

I had forgotten the doctor's strange pets. There was a cheetah, too; perhaps we might find it upon our shoulders at any moment. I confess that I felt easier in my mind when, after following Holmes's example and taking off my shoes, I found myself inside the bedroom. My companion noiselessly closed the shutters, moved the lamp onto the table, and looked round the room. All was as we had seen it in the daytime. Then creeping up to me and making a trumpet of his hand, he whispered into my ear again so gently that it was all that I could do to distinguish the words:

"The least sound would be fatal to our plans. We must sit without light. He would see it through the ventilator."

I nodded to show that I had heard.

"Do not go asleep; your very life may depend upon it. Have your pistol ready in case we should need it. I will sit on the side of the bed, and you in that chair."