L'action débute lors d'un banquet au manoir de Sir Hugo Baskerville. La scène illustre la cruauté de Sir Hugo qui, en pleine réception, tue dans un duel à l'épée un invité, Sir Bettans, qui avait courtisé sa femme. Alors que Sir Hugo va s'en prendre à cette dernière, un chien surgit et attaque le maître de maison, le mettant hors d'état de nuire.
Detective Morris Flynn (Hans Albers) and his assistant Macky McMacpherson (Heinz Rühmann), masquereading as Sherlock Holmes and Dr Watson, investigate two attractive sisters, Mary and Jane Berry, and the theft and forgery of valuable postage stamps.
A dinosaur skeleton is stolen from the "Museum of Unnatural History" so Hairlock Combs (a parody of Sherlock Holmes) and his assistant Dr. Gotsum disguise themselves as a horse and visit the scene of the crime. It is ultimately revealed that the thief is a concert xylophonist who is obsessed with using the skeleton as his instrument. Throughout the film, he repeats the phrase, "The best bones of all go to Symphony Hall!"
Jonathan Small, a prisoner serving a lengthy sentence on the Andaman Islands cuts a deal with two army officers, Major Sholto and Captain Morstan, in command of the prison. He reveals the location of a stash of loot in exchange for their help in helping him to escape from jail. The proceeds are to be split equally between the three of them.
Holmes is visited by Mr. Chalmers, an insurance agent with a strange tale. Seven elderly single men, calling themselves "The Good Comrades", live together in the remote Scottish castle of Drearcliffe House, near the village of Inverneill. Recently one of the "Good Comrades" received a strange message, an envelope containing nothing but seven orange pips. That night, he was murdered and his body horribly mutilated. A few days later, the second envelope was delivered, this time containing six pips, and the recipient also died mysteriously soon afterwards, his battered corpse being recovered from the base of the cliffs. Chalmers holds £100,000 of life insurance policies on the seven men, and suspects that one is systematically murdering the others in order to collect the money, and begs Holmes to investigate.
Justin Playfair (Scott) is a millionaire who retreats into fantasy after his wife's death, imagining himself to be Sherlock Holmes, the legendary fictional detective. Complete with deerstalker hat, pipe and violin, he spends his days in a homemade criminal laboratory, constantly paranoid about plots hatched by his (Holmes's) archenemy, Professor Moriarty.
Le Major Sholto a jadis pris possession du trésor caché par un Rajah, avec la complicité d'un de ses hommes et les informations données par Jonathan Small, un détenu. Mais il est rentré en Angleterre avec tout le butin.
The story takes place in 1913. Sherlock Holmes, virtually in retirement, is persuaded by Inspector Alec MacDonald of Scotland Yard to take on a baffling case. Three dead bodies have been found in London's East End, all with no discernible cause of death, but the expressions on their faces suggest that they all died in a state of terror.
Londres, 1900. Alors qu'il va enfin être pendu, le professeur Moriarty, cerveau du crime et ennemi juré de Sherlock Holmes, parvient à s'enfuir. Il reprend aussitôt ses activités criminelles en volant un code secret utilisé par l'armée anglaise pour chiffrer ses communications militaires, code qu'il essaie de revendre au plus offrant, une fois la clé en sa possession. Moriarty enlève donc le créateur du code, le seul à en avoir la clé. Malheureusement pour Moriarty, il s'agit de Mycroft Holmes, frère aîné de Sherlock et éminence grise des services secrets...
At the request of Inspector Lestrade (Colin Skinner), Sherlock Holmes (Patrick Macnee) investigates a double murder at the Strand Theatre, with the assistance of Dr John Watson (John Scott-Paget).
The great detective Sherlock Holmes and his trusted companion Dr. John Watson travel to New York City to investigate a recent threat made by Professor Moriarty.