Director Billy Wilder adds a new and intriguing twist to the personality of intrepid detective Sherlock Holmes. One thing hasn't changed however: Holmes' crime-solving talents. Holmes and Dr. Watson take on the case of a beautiful woman whose husband has vanished. The investigation proves strange indeed, involving six missing midgets, villainous monks, a Scottish castle, the Loch Ness monster, and covert naval experiments. Can the sleuths make sense of all this and solve the mystery?
Sherlock Holmes becomes involved in the case of Gabrielle Valladon when the young woman is fished out of the river and brought to 221b Baker Street by a cabbie. She's quite beautiful and doesn't really remember who she is or why she mentioned Holmes' name when found. Using his deductive powers, Holmes determines she is Belgian and having retrieved her luggage from Victoria station, that she had only recently arrived on the boat train. She came to England looking for her husband and has no idea how she ended up in the river. Soon however, the case becomes more complex when Holmes' brother Mycroft warns him to stay away and that it involves the security of realm. Undaunted, Holmes, Watson and Gabrielle follow the trail of clues and are soon in Inverness where they encounter both a troop of missing midgets - a case Holmes had earlier turned down - and have an encounter with the Loch Ness monster. Brother Mycroft also has some unexpected information for his brother.
When a bored Holmes eagerly takes the case of Gabrielle Valladon after an attempt on her life, the search for her missing husband leads to Loch Ness and the legendary monster.
- A dusty box is opened at a lawyers offices, fifty years after being sealed. The box contains Sherlock Holmes memorabilia, such as his cap, his pipe, his magnifying glass, a plaque with the number 221B, a hypodermic needle. Also in the box is a manuscript written by Dr. Watson. It records cases to be suppressed for fifty years because of their controversial [e.g. sexual] content or circumstances. The screen transitions back in time...
Sherlock Holmes (Robert Stephens) and Dr. Watson (Colin Blakely) are in their rooms at 221B Baker Street. Holmes complains he is bored, as he has no cases to work on, saying he needs a shot of 5% cocaine. Watson says, "Seven per cent", Holmes says he knows Watson disapproves and has been covertly diluting the solution.
Holmes, in a bad mood, complains that Watson's case histories, published in The Strand Magazine, exaggerate and embellish and are more lurid than reality. For example, he is barely six foot one, and Watson wrote that he is six foot four. Watson replies "Poetic license, Holmes!".
Still in a foul mood, Holmes yells at landlady Mrs. Hudson (Irene Handl) for dusting stuff on his desk. Later he has the rooms thick with smoke from using a machine to artificially smoke various cigarettes, as part of his research on cigarette ashes.
Watson suggests that he might consider investigating why six acrobatic midgets disappeared from their circus act, as a recent newspaper reports, but he is rebuffed. The next suggestion is that they go to a performance of a Russian ballet, since someone anonymously has sent them two expensive tickets.
At the end of the ballet, the impresario (Clive Revill) invites Holmes, and reluctantly, Watson, to a staff party. Watson parties with the dancers, while Holmes is led to the dressing room of star ballerina Madame Petrova (Tamara Toumanova). Petrova, speaking Russian, offers Holmes a Stradivarius violin in exchange for sex leading to her conceiving a child that might inherit her beauty and his intellect. Petrova says she has read The Hound of the Baskervilles, and also that he was not her first choice, but Tolstoy was too old to function, and Tchaikowski turned out to be not interested in women.
Holmes turns her down as delicately as he can, claiming that he and Watson are lovers who are not interested in women either. Petrova angrily throws him out.
Meanwhile Watson has been drinking, dancing a riotous storm arm in arm in a circle of beautiful ballerinas. The impresario whispers to one girl that Watson is homosexual, the news is spread from ear to ear, and the girls in the dancing circle are replaced by male dancers one by one. Watson, drunk, wearing a flower behind his ear, finally asks, "What happened to the girls?" and is led off to Baker Street by Holmes.
Watson berates Holmes for what he said, surmising that the rumour would never die off, particularly because Holmes is not known to have had any relations with women, whereas Watson has been married. Holmes says he wanted to spare Madame Petrova's feelings, doesn't care to have a reputation with women. Watson asked if he would be presumptious to presume Holmes had had affairs with women. Holmes says "You are being presumptuous" as he goes into his room.
Soon after, a cabbie rings at the door and wants to be paid. He fished a nearly drowned woman (Geneviève Page) out of the river, in shock, clutching a card with the Baker street address on it. As the cabbie leaves, a mysterious looking older man has been watching from a carriage in the street.
Watson convinces Holmes to take a look at her. She has received a blow on the head and is barely conscious. Holmes inspects her shoes and labels on her dress that indicate she is from Brussels. The card she was clutching is illegible from getting wet, but some ink has rubbed on her palm and Holmes reads the number 130 by looking at the mirror image. She is wearing a wedding ring with the names Gabrielle and Emil, but she appears too dazed to give information, although she speaks French. Watson volunteers his bed and sleeps on the couch, and Mrs. Hudson helps her to Watson's bedroom.
Not long after, Gabrielle gets up from the bed (totally naked, of course, since Mrs. Hudson is drying her clothes) but still confused. She goes to Holmes talking to him as though he were her beloved husband Emil, whom she has found at last, holding onto him with passion. She retreats to Sherlock Holmes' bed where he sees on her beckoning hands the letters he could not read from the cardboard piece he had found in her hand when they first meet. He views the lettering, deduced from her baggage, on her palm, she in apparent alarm, viewed with a mirror.
The next morning, Mrs. Hudson arrives with breakfast and is Victorianly horrified to see the naked woman on Holmes' bed. Holmes enters from the street carrying a trunk and a fancy parasol. He recognized the wet card as a possible check stub, and since she was Belgian she would have come on the boat train from the Continent and checked her things at Victoria Station. They break into her trunk and find her last name is Valladon.
When Gabrielle wakes, she is better and tells her story. Her husband was working in London and wrote to her often and regularly until a few weeks ago. He is an engineer by profession and said his employer was Jonah. She wrote to him at an address she remembers. She begs Holmes to find her missing husband. Quick research shows there is no English company with that name, and that the address is an abandoned building. Holmes has her write a letter to the address, planning to go spy there the next day and see who picks up the letter. In between these comings and goings, the mysterious older man on a cab is again on the street, and sees Gabrielle's parasol open and close, whereupon he departs.
The next day they break into the abandoned building, where they find a cage full of canaries and mysterious tracks but no footprints. They hide as a postman drops a letter in the slot, see an old lady in a wheelchair come feed the canaries from the alley, and porters who come pick up a load of canaries. The letter is left behind, and when they see it, it is addressed to Sherlock Holmes!
The letter is from Mycroft [Sherlock's smarter older brother] who orders him to come to Diogenes Club at once, and Sherlock complies.
At the meeting, Mycroft (Christopher Lee) orders Sherlock to drop the case, as he knows all about Valladon. Mycroft's insistence doesn't deter Holmes, as the Diogenes Club might be a front for a covert government operation. While they are arguing, Wiggins (Graham Armitage), the messenger at the Diogenes Club enters with an urgent message that requires a reply, and Sherlock hears it -- that the three boxes should be delivered to one location and the runner to another.
Back in Baker Street, Holmes decides to disregard Mycroft's orders [after all, he is enjoying Gabrielle's company]. The three take the overnight train to Scotland, where the locations mentioned by Mycroft are, disguised as Mr. and Mrs. Ashdown and their valet. In the night in the bedroom compartment they share, Gabrielle and Holmes trade confidences. Gabrielle asks whether he was ever in love, and Holmes says that he was all set to be married once, his fiancée died of influenza. The way things turned out he considers women to be unreliable and not to be trusted, which is not the same as not liking them. Meantime, in the second class carriage, Watson sits next to a group of monks who do not talk, apparently Trappists. The leader, whom we recognize as the mysterious watcher in Baker Street, is reading a Bible open to the Book of Jonah.
They check into a hotel at the shore of Loch Ness. The first location mentioned by Mycroft turns out to be a cemetery. The gravedigger (Sterling Holloway) mentions that one father and two children recently drowned in Loch Ness. He blames the monster.
In the next sequences, the clues pile up. Three coffins, one large, two small, arrive, and are buried. Soon four children show up to put flowers on the graves, but as we see their faces, they are not children, but midgets. When Holmes and Watson later dig up the large coffin and open it, Gabrielle shrieks, as we see a youngish man there and two dead canaries that have turned white. The dead man has a copper wedding ring that has turned green, matching Gabrielle's. Watson thinks he saw the Monster on the misty lake. Two suspicious porters deliver large demijohns labeled "Sulfuric Acid " to Urquhart Castle. Watson sees the squad of mysterious monks walking around. The trio gets on a rowboat to try to chase the Monster, which is also seen through the mist by Holmes and Gabrielle. Holmes borrows Watson's stethoscope, which is always hidden inside his hat, and listens to the sound of a motor running under water. They gain on it but their boat is pushed from below so they all fall into the loch. At the hotel that evening, Holmes receives a magnum of champagne and the coachman insists he must get into the carriage with him. He is driven to Urquhart Castle and told to go up some exterior stairs that have been covered with a red velvet runner leading up to some tents.
At the top of the stairs, Sherlock is met by his brother Mycroft, who first scolds him and then reveals the mystery. A submarine was being developed for the British Navy, with Mr. Valladon on the team. The project was called Jonah because the submarine was to be underwater for three days and three nights. Midgets were recruited as crewmen because they took up less space and needed less air. Sulfuric acid of the batteries accidentally got mixed with sea water, and the mixture released chlorine gas, which killed Valladon, two midgets and two canaries. It turned the canaries white and the copper ring green.
However, Gabrielle is not Mrs. Valladon but rather a top German spy named Ilse Hoffmanstal, sent to England with a crew of German sailors, disguised as monks, whose mission is to learn the whereabouts of the submarine and try to steal it. She sent them messages in Morse Code by opening and shutting her pink parasol. They have tricked Sherlock into locating the submarine project, and he fell for it because he became enamored of Gabrielle and could not think properly. When taken out for testing, the submarine was disguised as a sea monster.
Queen Victoria (Mollie Maureen) arrives for the christening of the craft with the champagne, but is "not amused" when she learns the details because it would kill people without warning from a concealed location, something unworthy of England, and she orders the project scrapped forthwith. Despite Mycroft's pleas that the Germans are developing their own terrible weapons, Zeppelins that could bomb London from the air, she repeats her orders and departs.
Before arresting Ilse, it is arranged that the submarine be left unguarded. The squad of monks steals the submarine and sails it off underwater, but it has been rigged to explode.
Meantime, Sherlock has returned to the hotel room, where Gabrielle is most fetchingly nude in bed, and we see her from the back as the Rokeby Venus. He is dejected, not only because he has been tricked and another woman and Mycroft have got the better of him, but because he had developed real affection for Gabrielle.
Ilse von Hoffmanstal is arrested, but will not go to prison, as she will be exchanged for a British spy at the German-Swiss border. As she is driven off the hotel, she Morse Codes Sherlock back with her parasol, "Auf Wiedersehen".
Some months later, Sherlock receives a letter from Mycroft, telling him that Ilse was arrested as a spy in Japan, tried and shot. She had been using the alias Mrs. Ashdown.
Saddened, the detective retreats to his room to seek solace in cocaine and his violin.