Forest Row in the Weald is the scene of a harpoon murder, and a young police inspector, Stanley Hopkins, asks Holmes, whom he admires, for help. Holmes has already determined that it would take a great deal of strength and skill to run a man through with a harpoon and embed it in the wall behind him.
Peter Carey, the 50-year-old victim and former master of the Sea Unicorn of Dundee, who lived with his wife and daughter, had a reputation for being violent. Carey did not sleep in the family house, but in a small cottage that he built some distance from the house, whose interior he had decorated to look like a sailor's cabin on a ship. This is where he was found harpooned. Hopkins could find no footprints or other physical evidence. However, a tobacco pouch made of sealskin and with the initials "P.C." was found at the scene, which was full of strong ship's tobacco. This is rather unusual, as Peter Carey—or "Black Peter" as people called him—seldom smoked. Indeed, Hopkins found no pipe in the cabin. Carey was found fully dressed, suggesting that he was expecting a visitor, and there was some rum laid out along with two dirty glasses. There were brandy and whisky, too, but neither had been touched. There was also a knife in its sheath at Carey's feet; Mrs. Carey has identified it as her husband's. A little notebook was also found at the scene. It contains the initials J. H. N. and the year 1883. It also says C. P. R. on the second page, which Holmes reckons stands for Canadian Pacific Railway. The first set of initials is likely a stockbroker's, as the little book is full of what appears to be stock exchange information.