“That is very helpful, Mr. Holmes. No doubt you are right. Wonderful! Wonderful! Do you carry the names of all the gun makers in the world in your memory?”

Holmes dismissed the subject with a wave.

“No doubt it is an American shotgun,” White Mason continued. “I seem to have read that a sawed-off shotgun is a weapon used in some parts of America. Apart from the name upon the barrel, the idea had occurred to me. There is some evidence, then, that this man who entered the house and killed its master was an American.”

MacDonald shook his head. “Man, you are surely travelling overfast,” said he. “I have heard no evidence yet that any stranger was ever in the house at all.”

“The open window, the blood on the sill, the queer card, the marks of boots in the corner, the gun!”

“Nothing there that could not have been arranged. Mr. Douglas was an American, or had lived long in America. So had Mr. Barker. You don’t need to import an American from outside in order to account for American doings.”

“Ames, the butler——”

“What about him? Is he reliable?”

“Ten years with Sir Charles Chandos—as solid as a rock. He has been with Doughlas ever since he took the Manor House five years ago. He has never seen a gun of this sort in the house.”

“The gun was made to conceal. That’s why the barrels were sawed. It would fit into any box. How could he swear there was no such gun in the house?”

“Well, anyhow, he had never seen one.”

MacDonald shook his obstinate Scotch head. “I’m not convinced yet that there was ever anyone in the house,” said he. “I’m asking you to conseedar” (his accent became more Aberdonian as he lost himself in his argument) “I’m asking you to conseedar what it involves if you suppose that this gun was ever brought into the house, and that all these strange things were done by a person from outside. Oh, man, it’s just inconceivable! It’s clean against common sense! I put it to you, Mr. Holmes, judging it by what we have heard.”

“Well, state your case, Mr. Mac,” said Holmes in his most judicial style.

“The man is not a burglar, supposing that he ever existed. The ring business and the card point to premeditated murder for some private reason. Very good. Here is a man who slips into a house with the deliberate intention of committing murder. He knows, if he knows anything, that he will have a deeficulty in making his escape, as the house is surrounded with water. What weapon would he choose? You would say the most silent in the world. Then he could hope when the deed was done to slip quickly from the window, to wade the moat, and to get away at his leisure. That’s understandable. But is it understandable that he should go out of his way to bring with him the most noisy weapon he could select, knowing well that it will fetch every human being in the house to the spot as quick as they can run, and that it is all odds that he will be seen before he can get across the moat? Is that credible, Mr. Holmes?”

“Well, you put the case strongly,” my friend replied thoughtfully. “It certainly needs a good deal of justification. May I ask, Mr. White Mason, whether you examined the farther side of the moat at once to see if there were any signs of the man having climbed out from the water?”

“There were no signs, Mr. Holmes. But it is a stone ledge, and one could hardly expect them.”