: In the estate of the owner of the famous racing stables, strange things happen before the competition. Sherlock Holmes discovers that a man is trying to hide the death of his sister, on whom he is financially dependent.

Sherlock Holmes is contacted by the horse trainer Sir Robert Norberton, who lives in the Shoscombe estate and owns the famous race stables. Sir Robert has never been married and lives on his estate with his sister, Lady Beatrice. The estate belonged to the late husband of the lady, and Sir Robert lives on a small rent owned by his sister.

Now strange things are happening on the estate. Sir Robert was head over heels in debt, his only hope was a victory at the races of his stallion Prince, England's best horse. The Prince has a half-brother, resembling him like two drops of water, but much weaker. To outwit those who secretly gather information about horses, Sir Robert takes him out for a walk instead of the Prince.

Lady Beatrice, who is no less horse-obsessed than her brother, has not entered the stable for a whole week, but only drives past in a carriage. Sir Robert himself spends all days in the stable, and nights in the old crypt in the park. It was then that the corpse of some strange person was discovered in the crypt, looking like a tramp, and a charred human bone was found in a central heating furnace.

Lady Beatrice's favorite spaniel began to howl at night, and the dog had to be given to a neighbor, the owner of the hotel. Lady Beatrice had difficulty moving around because of a sore heart, and Sir Robert, who was very tender with his sister, came to her room every evening. Now he doesn’t go there - the lady has started drinking. And recently, a quarrel broke out between a brother and sister over a maid lady who could not resist the charm of Sir Robert.

Sherlock Holmes with Dr. Watson travel to the Shoskomb estate under the guise of gentleman fishermen. Friends stay in 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 on the Shoskomb estate. Lady Beatrice locked herself in her room, went into a binge, and appears in public, only going for a walk. Sir Robert is obsessed with winning, as he fell into the clutches of usurers. Holmes suggests that Sir Robert killed his sister and is trying to hide it, since he depends on her financially.

Having asked the owner of the hotel a spaniel, the great detective goes for a walk. A lady carriage appears on the road. Two women are sitting in it - a young and an old woman, wrapped in a shawl. Watson stops the stroller while Holmes lowers the dog. Spaniel clutching his teeth at the skirt of an old woman who drives the dog away in a rude masculine voice.

Then the great detective goes to the crypt. The body of an old woman is in the sarcophagus. But there comes Sir Robert. In order not to deal with the police, he opens up to the great detective.For evidence, he brings a couple from the crew - a servant of Lady Beatrice and her husband.

Lady Beatrice passed away a week ago. So that lenders who would immediately take away their property, including the stable, did not find out, Sir Robert decided to give the husband a maid, an actor by profession, for his sister, and hide her body in a crypt before the races. But the spaniel, which howled, yearning for the mistress, interfered with the implementation of the plan.

The prince wins the derby, Sir Robert receives a significant amount and restores his position in high society. The police treat him condescendingly, but the incident casts a slight shadow on Sir Robert's reputation.