"That knife has been found near the Sprigg house."
Henry frowned.
"The last I saw of that knife, it was in Selby's hands," Burton continued. "Well, what of it?"
"How did it come to be under the Sprigg ruins? You must help me to work that out. You are suspected of firing the house,--you know that, don't you?"
Henry's eyes fell. "Who says so?" he asked doggedly, but without spirit. "Selby does."
But this time he drew nothing. Henry merely shrugged his shoulders.
"The knife is the only direct link with you," Burton went on. "Therefore we must explain the knife. How did it get there?"
"What do I know about it? Or about anything?" Henry asked impatiently.
But Burton was persistent. "There are two possible theories," he said, watching Henry as he spoke. "The knife may have been left in the surgery when the committee departed, and the incendiary may have found it there and carried it off. I have reasons for believing that some one tried to enter--or rather, did enter--that room in the night. Or, as an alternative theory, Selby may have carried it away with him, either intentionally or unconsciously, and then dropped it near the Sprigg house,--either intentionally or unconsciously."
Henry listened with little softening of the bitterness in his face. "There is another possible theory," he said, with something like a sneer. "I may be lying when I say he didn't give the knife back to me."