For a long time no one spoke. The body of Silas Blackburn had been alone in a locked room, yet before their eyes it lay, turned on its side, as if to inform them of the fashion of this murder. The tiny hole at the base of the brain, the blood-stain on the pillow, which the head had concealed, offered their mute and ghastly testimony.
Doctor Groom was the first to relax. He raised his great, hairy hand to the bed-post and grasped it. His rumbling voice lacked its usual authority. It vibrated with a childish wonder:
"I'm reminded that it isn't the first time there's been blood from a man's head on that pillow."
Katherine nodded.
"What do you mean?" the detective snarled. "There's only one answer to this. There must have been a mechanical post-mortem reaction."
For a moment Doctor Groom's laugh filled the old room. It ceased abruptly. He shook his head.
"Don't be a fool, Mr. Policeman. At the most conservative estimate this man has been dead more than thirteen hours. Even a few instants after death the human body is incapable of any such reaction."
"What then?" the detective asked. "Some one of us, or one of the servants, must have overcome the locks again and deliberately disturbed the body. That must be so, but I don't get the motive."
"It isn't so," Doctor Groom answered bluntly.
Already the detective had to a large extent controlled his bewilderment.