Knapp, who was really of a cold and unimpressionable temperament, refrained from further argument, and confined himself to watching the young man, whose movements seemed to fascinate him.

“Astonishing!” Mr. Fenton heard him mutter to himself.  “He’s more like an eel than a man.”  And indeed the way Sweetwater wound himself out and in through that room, seeing everything that came under his eye, was a sight well worth any professional’s attention.  Pausing before the dead man on the floor, he held the lantern close to the white, worn face.  “Ha!” said he, picking something from the long beard, “here’s a crumb of that same bread.  Did you see that, Mr. Knapp?”

The question was so sudden and so sharp that the detective came near replying to it; but he bethought himself, and said nothing.

“That settles which of the two gnawed the loaf,” continued Sweetwater.

The next minute he was hovering over the still more pathetic figure of John, sitting in the chair.

“Sad!  Sad!” he murmured.

Suddenly he laid his finger on a small rent in the old man’s faded vest.  “You saw this, of course,” said he, with a quick glance over his shoulder at the silent detective.

No answer, as before.

“It’s a new slit,” declared the officious youth, looking closer, “and—­yes—­there’s blood on its edges.  Here, take the lantern, Mr. Fenton, I must see how the skin looks underneath.  Oh, gentlemen, no shirt!  The poorest dockhand has a shirt!  Brocaded vest and no shirt; but he’s past our pity now.  Ah, only a bruise over the heart.  Sirs, what did you make out of this?”

As none of them had even seen it, Knapp was not the only one to remain silent.

“Shall I tell you what I make out of it?” said the lad, rising hurriedly from the floor, which he had as hurriedly examined.  “This old man has tried to take his life with the dagger already wet with the blood of Agatha Webb.  But his arm was too feeble.  The point only pierced the vest, wiping off a little blood in its passage, then the weapon fell from his hand and struck the floor, as you will see by the fresh dent in the old board I am standing on.  Have you anything to say against these simple deductions?”

Again the detective opened his lips and might have spoken, but Sweetwater gave him no chance.

“Where is the letter he was writing?” he demanded.  “Have any of you seen any paper lying about here?”

“He was not writing,” objected Knapp; “he was reading; reading in that old Bible you see there.”

Sweetwater caught up the book, looked it over, and laid it down, with that same curious twinkle of his eye they had noted in him before.

“He was writing,” he insisted.  “See, here is his pencil.”  And he showed them the battered end of a small lead-pencil lying on the edge of his chair.

“Writing at some time,” admitted Knapp.

“Writing just before the deed,” insisted Sweetwater.  “Look at the fingers of his right hand.  They have not moved since the pencil fell out of them.”