"Imagination bridges the intervals between facts," Quarles answered. "We get again to a fact--the iron-bound chest. It links the two men together. I have no doubt the file seller knew of its peculiar mechanism as well as Portman did. You could not open it, and, since the key was in the lock, no mystery about it, you naturally did not think it of much importance. When together we succeeded in opening it I found on the floor of it a tiny stain. I thought it was a blood stain, but I was not sure. At any rate, the measurements of the chest were such that a body might be pressed in it. Frankly, I admit I expected to see Portman's body when we raised the lid. For the sake of some documents--it is impossible to say what they were--I believed this file seller had murdered Portman, taken his key, opened the safe, taken the papers he wanted, thrust the body into the chest, and had then departed in the character of his victim, flinging the safe key under the bookcase as he went. As there was no body I wondered whether Mrs. Eccles or the clerk, or both, were accomplices of the murderer; whether that chest might not conceal a secret entrance to the room. The idea did not fit my theory very well, but I laid a trap, and you know the result, Wigan. The action of shutting that chest opens the bottom of it, so that whatever is placed in it falls out as soon as the lid is closed and locked. I believe the body of Portman was in it and had got caught somehow--that was why you could not open it, why we could not open it until we had hammered it about, and by constant working upon the lid had released the body. I feel certain that chest had its home in Florence; that is why I suggest an Italian may be the criminal. He may have been long resident in England, of course; certainly he is a man who speaks English perfectly, or the clerk would have described him as a foreigner." "But the body--where is it?" I asked. "I've been to the British Museum to-day," said Quarles, taking up the rough sketch from his desk. "This is a copy of an old map of the Finsbury district, and here I find was one of the old plague pits. I believe Portman's house stands on this plot." It was a very rough sketch, but, as I compared the place the professor had indicated with the old landmarks and their modern equivalents which he had marked, there could be little doubt that Quarles was right.