“You put it very clearly,” said Holmes.  “I am inclined to agree with you.”

“Well, then, we are driven back to the theory that it was done by someone from outside.  We are still faced with some big difficulties; but anyhow they have ceased to be impossibilities.  The man got into the house between four-thirty and six; that is to say, between dusk and the time when the bridge was raised.  There had been some visitors, and the door was open; so there was nothing to prevent him.  He may have been a common burglar, or he may have had some private grudge against Mr. Douglas.  Since Mr. Douglas has spent most of his life in America, and this shotgun seems to be an American weapon, it would seem that the private grudge is the more likely theory.  He slipped into this room because it was the first he came to, and he hid behind the curtain.  There he remained until past eleven at night.  At that time Mr. Douglas entered the room.  It was a short interview, if there were any interview at all; for Mrs. Douglas declares that her husband had not left her more than a few minutes when she heard the shot.”

“The candle shows that,” said Holmes.

“Exactly.  The candle, which was a new one, is not burned more than half an inch.  He must have placed it on the table before he was attacked; otherwise, of course, it would have fallen when he fell.  This shows that he was not attacked the instant that he entered the room.  When Mr. Barker arrived the candle was lit and the lamp was out.”

“That’s all clear enough.”

“Well, now, we can reconstruct things on those lines.  Mr. Douglas enters the room.  He puts down the candle.  A man appears from behind the curtain.  He is armed with this gun.  He demands the wedding ring—­Heaven only knows why, but so it must have been.  Mr. Douglas gave it up.  Then either in cold blood or in the course of a struggle—­Douglas may have gripped the hammer that was found upon the mat—­he shot Douglas in this horrible way.  He dropped his gun and also it would seem this queer card—­V.V. 341, whatever that may mean—­and he made his escape through the window and across the moat at the very moment when Cecil Barker was discovering the crime.  How’s that, Mr. Holmes?”

“Very interesting, but just a little unconvincing.”

“Man, it would be absolute nonsense if it wasn’t that anything else is even worse!” cried MacDonald.  “Somebody killed the man, and whoever it was I could clearly prove to you that he should have done it some other way.  What does he mean by allowing his retreat to be cut off like that?  What does he mean by using a shotgun when silence was his one chance of escape?  Come, Mr. Holmes, it’s up to you to give us a lead, since you say Mr. White Mason’s theory is unconvincing.”

Holmes had sat intently observant during this long discussion, missing no word that was said, with his keen eyes darting to right and to left, and his forehead wrinkled with speculation.