This is the last of the Sherlock Holmes stories. This book shows Holmes getting a message from Porlock (who works for Moriarty). However, Porlock is a sort of double agent in that he gives Holmes a lot of additional information on Moriarty throughout the novels. EVen though he can't prove it, Holmes knows that Moriarty is the one contorlling the underworld operations. Porlock's message is that there is a man named Doublas who is in danger. They are too late, though, as the inspector from Scotland Yard calls Holmes to ask for his help solving the murder of Mr. Doublas of Birlstone Manor. Douglas had been murdered at night and was shot in teh head. A man named Cecil Barker was staying at the house on the night of the murder and was a regular guest. A sawed off shotgun was found to be the weapon and was fired at close range.
Barker says that he heard the shot and ran downstairs immediately. Teh drwabridge was up and says that he lowered it to get help. There is blood on the window sill where someone might have enetered. Beside the body was found a card with the initials V.V on it. There is a small brand on the man's arm, but it is old. He is missing his wedding ring.
Holmes remarks that he finds it unusual that Mrs. Douglas showed so little emotion at finding that her husband was dead. Barker offers that he believes that a secret society of men pursued Douglas and that living in the country was his way of avoiding them. They are somehow connected to 'the valley of fear'.
Doing what Holmes is good at doing, he deduces that Barker made the mark on the windowsill with his shoe. The police learn that there is an American staying at a guest house. The gun is American as well, and it would seem that they have their man. However, Holmes is not convinced. He has the inspector contact Barker to tell him that they are going to dredge the moat the next day, then Holmes, Watson and the inspector stake out the moat. Surely, Barker appears and tries fishing something out of the moat.
Just as they are about to arrest Barker, Mr. Douglas appears, alive and well...shocking everyone. He states that he had spotted one of his enemies from the valley of fear, and that he'd struggled with the same assailant that evening. The man was killed, so with Barker's help, they dressed the assailant in Douglas's clothing and left him to be found. Douglas had at one time been a detective for the Pinkerton's, and when he had infiltrated a gang in Vermissa Valley (the valley of fear) the criminals vowed to get even. Holmes tells him that if he values his life, he will leave immediately. Holmes suspects that Moriarty was behind the assailant's attack and that more will be forthcoming. Douglas and his wife set out for Africa, but they fall overboard before reaching Africa.