On 24 October 1891, Dr. John H. Watson receives a telegram from his former landlady asking him to see Sherlock Holmes, the great detective. When Watson arrives, Holmes is paranoid. He points a gun at Watson while raving about the evils of Professor James Moriarty, whom he believes is the "Napoleon of Crime." After finding a syringe of cocaine, Watson returns home and is visited by Professor Moriarty, who complains that Holmes is stalking him and sending him threatening letters. Moriarty then explains that he was a math tutor to Holmes and his brother, Mycroft, until "the tragedy." When Watson asks what he means, Moriarty grows anxious and says he would not have come if he thought Holmes had not revealed the secret, and flees. With the help of Mycroft, Watson convinces Moriarty to go to Dr. Sigmund Freud’s house in Vienna, Austria, so Holmes will follow thinking the Professor is in the act of committing a great crime, thereby hoping to initiate psychiatric sessions between Holmes and the doctor. Holmes takes the bait and with Toby, his bloodhound, follows Moriarty across Europe. On the way, they run into The Pasha, ruler of the Ottoman Empire. When they get to Vienna, Toby follows Moriarty’s scent and leads them to Freud’s house. Holmes accuses Freud of being Moriarty in disguise, but Freud tells Holmes that Moriarty is gone and that he will be receiving psychological treatment. Holmes claims he is incurable, but Freud convinces him that he can help and uses hypnosis to reduce the pain of drug withdrawal. For several days, Holmes suffer delusions in which he sees a rabid dog, a group of redheaded men, and a bell rope turning into a viper. During this time, Freud explains his theories of the unconscious to Watson, claiming that Holmes’s addictions are rooted in a past trauma and, unless they can discover the cause, Holmes will slip back into drug use. One morning, Holmes realizes he was wrong about Moriarty. Freud proclaims the worst is over and invites Watson to take a break by joining him at his gym. There they run into Baron Von Leinsdorf, who makes anti-Semitic remarks and asks Freud if he made love to his mother. After Watson throws wine in the Baron’s face, the Baron challenges Freud to a duel. As the injured party, Freud is permitted to pick the time and weapon; he selects the present moment and tennis rackets. On the tennis court, the Baron easily wins the first two matches. Freud analyzes the Baron’s play, concludes he has no backhand, and Freud plays to the Baron’s weakness to defeat him. A few days later, Freud receives a message that Lola Deveraux, a past patient and the former toast of Europe, has attempted suicide. With Watson and Holmes, Freud goes to the hospital, unaware that the Baron’s coach is waiting nearby. They find Lola under sedation and Freud explains that his patient was also a cocaine addict, but Holmes deduces she did not relapse willingly. He points to bruises on her wrists and ankles, indicating she was bound. The scrapes on her hand suggest that she climbed down a water pipe. He concludes that her supposed suicide attempt was actually a result of avoiding recapture. When Lola awakens, she explains that she was kidnapped on her way to meet the Baron. She has no idea why she was abducted, but describes the man who kidnapped her in great detail. Later, in a restaurant, Holmes insists he is too sick to help Lola and begs Freud to hypnotize again him to fight withdrawals. Freud agrees, but only if Holmes tells him what he will do next if he takes the case. Holmes tells Freud that the very man Lola described is also following them. Before Freud can hypnotize Holmes, however, the follower gets up and leaves. Holmes realizes they are being led on a wild goose chase, but the man is their only lead, so they follow him. They are led into the Spanish Riding School where Holmes is overwhelmed by withdrawals. As Freud hypnotizes Holmes, a team of Lipizzan stallions appears. Freud screams that the horses have been trained to kill, and Watson distracts the animals until Holmes can be brought out of his trance. Holmes then tricks the horses into running through a gate. He yells that Lola is in danger and runs away before Watson or Freud can ask questions. The Baron arrives at the hospital with an armful of lilies and tells Lola that Freud said she is to go with him. He also says that after being held in a cold warehouse, she needs a warm bed. Lola realizes she never told anyone where she was held, but before she can decide what to do, a nun comes in and the Baron orders her to assist him in getting Lola down to his coach. When Holmes finds Lola missing, he orders Freud home to get Toby. Holmes finds lilies scattered along the hall. He follows Lola’s trail with Watson to a brothel, where they are surprised to find Freud sitting on a bed with the murdered nun. The doctor explains that he realized the best place to hide a courtesan is amongst a bevy of courtesans. Holmes deduces that there was no struggle at the hospital because Lola knew her kidnapper; the Baron. Because a curved knife caused the nun’s wounds and he finds a Turkish cigarette with a few strands of a Persian carpet, Holmes realizes the Pasha is holding Lola. The man they followed comes into the room and is captured by Watson. He confirms that the Baron kidnapped Lola for the Pasha’s harem and is now on their way to Istanbul, Turkey. Holmes, Freud and Watson arrive at the station to find the Pasha’s train has already left. Watson uses his revolver to persuade a stationmaster to help hijack another train, and they race across Austria to stop the Pasha before he can get to the international border. They catch up to the Pasha’s train, but not before it crosses the border. Guards drop the gates, but Holmes’s train smashes through and keeps going. Meanwhile, the Baron uncouples his last car to block Holmes’s train. The stationmaster pushes the car forward until it almost touches the other train. Holmes borrows Watson’s revolver, leaps to the lead train, and confronts the Baron, who challenges him to a swordfight. Soon, they battle all over the train, and end on the roof. Freud jumps to the next train, finds a rifle, and faces the Pasha and two bodyguards. The Pasha tells Freud to throw down his gun or be killed. The doctor vows to kill the Pasha before his men can reach him and the Turk surrenders. Meanwhile, Holmes is losing his fight until Watson yells, a reminder that the Baron has no backhand. Holmes ducks a blow and stabs the Baron. Later, as Holmes and Watson leave Vienna, Holmes asks how he can repay Freud, and the doctor asks to hypnotize the detective one more time. In a trance, Holmes reveals that as a little boy, he discovered his mother in bed with Moriarty, when his father came in and killed his mother. Freud brings Holmes out of the trance, and says that the detective did not say anything while he was hypnotized. Holmes tells Watson he needs to be alone to complete his recovery instead of returning to London, and suggests that Watson should write that his math tutor murdered him. Holmes then embarks on a riverboat tour of the Danube River. On the viewing deck, he is surprised, but pleased to find Lola. The two flirt as the boat travels down river.