Sherlock Holmes is approached for help by the horse trainer Sir Robert Norberton, who lives in the estate of Shoscombe and is the owner of the famous race stables. Sir Robert was never married and lives in his estate with his sister, Lady Beatrice. The estate belonged to the late lady husband, and Sir Robert lives on a small rent owned by his sister.
Now strange things are happening in the estate. Sir Robert is in debt, in debt, his only hope is the victory at the races of his prince Prince, the best horse of England. The Prince has a half-brother, like him as two drops of water, but much weaker. To outwit those who secretly collect information about horses, Sir Robert takes him out for walks instead of the Prince.
Lady Beatrice, who is as crazy as a brother, has not been to the stables for a week, but only passes by in the carriage. Sir Robert himself spends his days in the stable, and the nights are in the old crypt in the park. It was then that a corpse of some strange person was discovered in the crypt, in the form of a tramp, and in a central heating furnace a charred human bone was found.
The favorite spaniel Lady Beatrice began to howl at night, and the dog had to give to the neighbor, the hotel owner. Because of a sick heart, Lady Beatrice can hardly move, and Sir Robert, who relates to her sister with great affection, came to her room every evening. Now he does not go there – the lady started drinking. And recently there was a quarrel between brother and sister over the maid lady, who could not stand the charm of Sir Robert.
Sherlock Holmes and Dr. Watson travel to the estate of Shoscombe under the... guise of fishermen-gentlemen. Friends stop at a nearby hotel. After talking with them, the owner says that Sir Robert gave him a very expensive spaniel.
The great detective weighs the facts. A week ago, something happened in the estate Shoscombe. Lady Beatrice locked herself in her room, went into a binge, and in public shows, only going for a walk. Sir Robert is hooked on winning, as he fell into the hands of pawnbrokers. Holmes suggests that Sir Robert killed his sister and tries to hide it, because it depends on it financially.
Asking the host hotel spaniel, the great detective goes for a walk. A lady’s carriage appears on the road. There are two women sitting in it – young and elderly, wrapped in a shawl. Watson stops the carriage, and Holmes takes the dog down. The spaniel grasps his teeth over the skirt of an old woman who drives the dog away in a rough man’s voice.
Then the great detective goes to the crypt. In the sarcophagus is the body of an old woman. But there comes Sir Robert. In order not to deal with the police, he opens a great detective. For the testimony, he leads a couple of the crew – the maid of Lady Beatrice and her husband.
Lady Beatrice passed away a week ago. So that creditors who will immediately take away property, including the stable, Sir Robert decided to give the maid of the maid, the actor by profession, for his sister, and hide her body in the crypt. But the plan was hampered by the spaniel, who howled, yearning for the mistress.
The Prince wins the derby, Sir Robert gets a considerable amount and restores his position in the high world. The police treat him condescendingly, but the incident casts a slight shadow on Sir Robert’s reputation.