“You are coming, I suppose, Jervis?” said Thorndyke.
“If I shall be of any use,” I replied.
“Of course you will,” said he. “Two heads are better than one, and, by the look of things, I should say that ours will be the only ones with any sense in them. We will take the research case, of course, and we may as well have a camera with us. I see there is a train from Charing Cross in twenty minutes.”
For the first half-hour of the journey Thorndyke sat in his corner, alternately conning over his notes and gazing with thoughtful eyes out of the window. I could see that the case pleased him, and was careful not to break in upon his train of thought. Presently, however, he put away his notes and began to fill his pipe with a more companionable air, and then the inspector, who had been wriggling with impatience, opened fire.
“So you think, sir, that you see a way out for Ellis?”
“I think there is a case for the defence,” replied Thorndyke. “In fact, I call the evidence against him rather flimsy.”
The inspector gasped. “But the knife, sir? What about the knife?”
“Well,” said Thorndyke, “what about the knife? Whose knife was it? You don’t know. It was covered with blood. Whose blood? You don’t know. Let us assume, for the sake of argument, that it was the murderer’s knife. Then the blood on it was Pratt’s blood. But if it was Pratt’s blood, when the hounds had smelt it they should have led you to Pratt’s body, for blood gives a very strong scent. But they did not. They ignored the body. The inference seems to be that the blood on the knife was not Pratt’s blood.”
The inspector took off his cap and gently scratched the back of his head. “You’re perfectly right, sir,” he said. “I’d never thought of that. None of us had.”
“Then,” pursued Thorndyke, “let us assume that the knife was Pratt’s. If so, it would seem to have been used in self-defence. But this was a Norwegian knife, a clumsy tool—not a weapon at all—which takes an appreciable time to open and requires the use of two free hands. Now, had Pratt both hands free? Certainly not after the attack had commenced. There were seven wounds, all on the left side of the back; which indicates that he held the murderer locked in his arms and that the murderer’s arms were around him. Also, incidentally, that the murderer is right-handed. But, still, let us assume that the knife was Pratt’s. Then the blood on it was that of the murderer. Then the murderer must have been wounded. But Ellis was not wounded. Then Ellis is not the murderer. The knife doesn’t help us at all.”