: After a three-year absence, Sherlock Holmes returns and, with the help of a cunning trap, deals with the first assistant of the deceased professor Moriarty.

Three years have passed since the death of Sherlock Holmes. In London, under very mysterious circumstances, the young Earl Ronald Adair was killed. Ronald was a fan of the card game and was a member of several clubs. A month and a half before his death, Ronald paired with Colonel Moran won a large sum.

That fateful evening, he again played with Colonel Moran, but lost a little. Arriving home, Ronald locked himself in his room, where the window was open. Mother and sister were not at home. When they returned and knocked on Ronald, no one answered. Hacking the door, they saw that the young man was dead - they shot him in the head. On the table lay money and a sheet counting card wins and losses. No traces were found, no one heard the shot. They could shoot through the window, but it opens onto a crowded street, and the killer could not go unnoticed. The young man had no enemies, and the money and valuables that were in the room remained untouched.

Using the theory of his friend, the great detective Sherlock Holmes, Dr. Watson is trying to solve the riddle. While walking in the park, he accidentally pushes a hunched old man holding several books.Watson helps the old man pick up books, but he angrily mutters something in return. At home, he finds the same old man who came to apologize for his rudeness. In amazement, Dr. Watson sees that the old man is none other than his friend Sherlock Holmes.

Left alone near the waterfall, Sherlock Holmes met with Professor Moriarty. Applying the baritsu fighting techniques, the great detective won the fight, pushing the professor into the abyss. Knowing that the professor’s accomplices were nearby, Holmes hid himself, imitating his death. All this time he was hiding, but returned to investigate the murder of Count Adler.

Holmes leads Watson to an empty house across from his apartment on Baker Street. Watson sees in the window a man sitting in an armchair, whose outlines resemble the great detective. Holmes reveals a secret: this is a waxwork made to order. So that there is no doubt that this is a living person, the landlady, Mrs. Hudson, periodically imperceptibly changes her position.

A person comes into the house, sneaks, opens a window and shoots a wax figure from a gun. With the help of Watson and the police, Holmes neutralizes the criminal. Prisoner is Colonel Moran, the right hand of the late professor Moriarty, the owner of a unique silent air gun, from which Ronald Adler was shot. Playing in tandem with Moran, the young man discovered that Moran is a sharpie. Ronald did not dare to publicly accuse the colonel, and most likely threatened to expose him in private.

The police leads the colonel, who whispers with hatred all the time: “Devil! The cunning devil! "