Plot

The master sleuth hunts his archenemy, Professor Moriarty, who is planning the crime of the century.

When Sherlock Holmes arrives in court moments too late to give evidence against Professor Moriarty, the professor is acquitted. Soon afterward, he develops a scheme for stealing the crown jewels from the Tower of London. In order to get Holmes involved, he persuades a gaucho flute player to murder a girl.—Ed Stephan <stephan@cc.wwu.edu>

The second, and last, of the Twentieth Century-Fox Rathbone/Bruce Sherlock Holmes movies opens with the 20th Century Fox logo and theme, followed by title and credits shown over a pipe-smoking Basil Rathbone in silhouette. A hand opens a book, signed by Sherlock Holmes, and dated 9 May, 1894. It briefly explains that Professor Moriarty is a most dangerous criminal. The criminal case of Professor Moriarty (George Zucco) is completed, and due to a lack of evidence, he is found not guilty. The Justice of the Court (Holmes Herbert) is appalled and says, "It is undoubtedly a gross miscarriage of justice." Sherlock Holmes (Basil Rathbone) bursts into the packed courtroom with new evidence against Moriarty, but he is too late. Holmes exits the courthouse and the Professor is waiting for him. They share a cab to 221B Baker Street. Moriarty gloats and provides Holmes with a challenge. He boasts that he will commit the crime of the century and Holmes will be discredited.

At the Professor's home, Moriarty tends to some flowers in the greenhouse. A South American musician plays what will later be determined to be an Inca Funeral dirge. The butler, Dawes (Frank Dawson) replies to summons and tells his boss that Mr. Bassick has arrived. Bassick (Arthur Hohl) enters the study and is handed a letter to post. Curiosity, on the part of Bassick, provides a few more clues to the crime of the century, one of which, involves Sir Ronald Ramsgate, Constable of the Tower of London. After Bassick leaves, Moriarty turns his wrath on Dawes for not watering his plants.

In Sherlock Holmes' room at Baker Street, he is plucking at a violin trying to find the note that will act as a fly repellant. Mrs. Hudson (Mary Gordon) removes the tea service. She gives Billy (Terry Kilburn) his cleaning instructions. He sweeps the dirt under the rug and then peers over the banister to see who's at the door. Dr. Watson (Nigel Bruce) has arrived. He walks upstairs to see Holmes. Holmes briefs Watson on a letter he got from a young lady by the name of Miss Brandon. Sir Ronald Ramsgate (Henry Stephenson) pays a call on the detective to ask his help on securing the delivery of the Star of Delhi to the tower's crown jewel collection. Ramsgate received a letter warning that it would not reach its destination. A knock at the door sends Watson over to answer it. A young lady, Ann Brandon (Ida Lupino) enters quickly. She slams the door shut and runs to the window. She tells Holmes that she was followed. Sir Ronald exits the room. Ann tells Holmes her story and her fear of murder. She shows Holmes a picture her brother received of a man with a bird hung around his neck, dated May 11. She explains that her father was murdered ten years earlier to the day. Watson answers another knock at the door. It is Ann's lawyer and fiancé, Jerrold Hunter (Alan Marshal). He is upset that she consulted with Sherlock Holmes. Holmes agrees to take her case. Holmes examines the picture again and notes, "I think it belongs to the Procellariiformes family." He proposes to go to the Kensington Museum for more research. Holmes asks Watson to check on Hunter. At the Kensington Museum, Holmes discovers the bird is an albatross and is reminded of the Samuel Taylor Coleridge poem from 1798, The Rime of the Ancient Mariner.

Watson discovers Moriarty consulting with Hunter and follows the professor outside. Ann's brother, Lloyd Brandon (Peter Willes) enters Hunter's office and complains the note is causing him great anxiety. Lloyd walks home. Hunter arms himself and follows Lloyd at a discreet distance. Watson finds Holmes and Miss Brandon at the Museum and they quickly depart to save Lloyd. They take a cab to the Brandon residence. Lloyd passes through a park. Hunter follows closely, but too late as Lloyd screams. The cab pulls up and Ann sees her brother's body. Ann is carried home by Holmes. The house is across the street from the park.

Holmes walks into a large room where Inspector Bristol (E.E. Clive) is questioning Hunter about Lloyd's murder. Bristol is convinced that Hunter is the culprit and intends to arrest him. Holmes convinces Bristol to delay any action as Lloyd died of strangulation, not having the back of his skull broken. Watson and Ann enter the room, and she grows more suspicious of Hunter's involvement. Holmes and Watson go to the park to look for clues. Watson lays in the street, as directed by Holmes, on an "x" to mark the spot where Lloyd died. An inquisitive stranger (William Austin) happens along and sees Watson in the gutter. He is concerned Watson needs a doctor and is sent packing by an annoyed Watson. Holmes calls and shows Watson a club footed man's footprints, a broken branch, and a chinchilla's foot charm or watch fob. Ann enters the room that contains her brother's body. She hears the weird music coming from the street below her window. She screams and the man playing rushes away in a cab. Holmes and Watson run from the park to the Brandon residence. She is able to play the tune for Holmes. She heard the tune once before in South America when her father was killed.

At Baker Street, Holmes transcribes the tune. Billy expresses interest in the chinchilla's foot. He tells Holmes that it must be a good luck charm in Chile or Bolivia. Holmes identifies the tune. Sir Ronald drops by again. He asks about the note and the emerald's arrival the next day. He asks Holmes to be there personally. Ann drops by to show Holmes another drawing like the one her brother received, except the date is May 13 on her drawing. Holmes advises Ann to go to the Conyngham's party. Watson reminds Holmes he has two appointments for the next day, so Holmes delegates the jewel transfer case to Watson.

Dawes shaves his boss, providing the professor with a disguise of sorts. Moriarty takes the cab driven by Bassick. Bassick confirms the jewel is being delivered. Ann arrives at the party and is greet by Lady Conyngham (Mary Forbes). Lady Conyngham insists Ann spend the weekend. Tony Conyngham (Anthony Kemble-Cooper) escorts Ann out onto the terrace. They watch a music hall entertainer (Holmes in disguise) singing a ditty about a sea shore holiday. Holmes/Singer approaches Ann. She doesn't recognize the detective at first, but then she does. Holmes warns her to be vigilant. One of the gaucho players in the band, Mateo (George Regas), plays his flute and eyes Ann.

At the tower, Sir Ronald is annoyed that Holmes sent Watson. Three policemen arrive. Sgt. Bullfinch, Moriarty in disguise, demands to see Watson's identification. The Royal Navy delegation delivers the Star of Delhi emerald to Sir Ronald. Sir Ronald returns to the Tower and goes to place the jewel in the locked case. The lights go out and a search is made for the crooks and the stolen jewel. The emerald is quickly located and is placed in the case. What Sir Ronald and Watson fail to notice is that Moriarty is in the case with the Crown Jewels. Moriarty fixed the lock to allow himself escape from the locked case. The party has ended and Lady Conyngham escorts Ann up to her room. She hears the weird tune from under her window. She goes out to investigate. Ann runs outside to find Hunter waiting. She recoils from Hunter's approach. She runs away through the garden. She is followed by Hunter who encounters Mateo. Mateo dispatches Hunter with a club to the head. Mateo plays his tune and chases Ann. He pulls out a deadly set of bolos, but Holmes pulls her to safety before the weapon can kill her. Holmes shoots Mateo as Watson arrives on the scene. Mateo confesses his part in the crime, but he names Moriarty as assisting.

Holmes and Watson break into the professor's house. There they find the clues to the Tower and drive a cab to the Tower to stop the theft of the Crown Jewels. Rolling the cab causes the guard to exit the Tower to assist after the accident. This allows Holmes entrance to the Tower. Moriarty is distracted by the noise and he stops his theft of the jewels to kill Holmes. They run about the place shooting at each other. Holmes leads his quarry upstairs to the roof. They struggle and Moriarty is struck repeatedly and falls over the battlement wall to his death below.

At a pub, Watson reads the wedding announcement of Ann and Hunter to Sherlock Holmes. They are celebrating the end of another case. Holmes asks to borrow a violin to rid himself of a pesky fly. Watson picks up the newspaper, folds it a few times and swats the fly. Holmes exclaims, "Very effective my dear Watson." Watson replies, "Elementary, my dear Holmes, elementary." We close with the Cast Credits.