Sir Charles Farnsworth is found dead in his mysterious Farnsworth Castle. It turns out that Farnsworth had a clause inserted in this will that his death, no matter what the apparent cause, would be investigated by Sherlock Holmes. Holmes' investigation reveals traces of arsenic in the man's body, and there seems to be no shortage of people who knew Sir Charles who wanted him dead.

After a famous criminal is run over and killed by a milk truck, Insp. Lestrade finds a mysterious coded note in the man's clothing. He asks Holmes to decipher it, and Holmes' subsequent investigation leads him to assume the dead gangster's identity and he follows a trail of clues to Paris.

Holmes and Watson return from a vacation at Brighton to find an impostor has been impersonating Holmes, misadvising Lestrade to guard Hambleburg's not Carrolton's jewelry store and Sir Arthur to hide his valuables in the biscuit jar. Fighting impersonation with impersonation, Watson becomes the maharaja of Gampoor.

Jessie Hooper hires Holmes to find her missing husband, William, and -- with the help of Lestrade's cousin MacDougal of Glasgow -- he his found hung -- like his grandfather. A rope salesman's laugh is the key clue. It is ironically the window that William never returned to repair that traps villain by his tie.

Russell Partridge announces to his wife Janet one day that he is in fact a killer who has murdered his six previous wives, and notifies her that she has one day to live and get her affairs in order before he murders her, too. Janet can get no one to believe her tale, except Holmes and Watson, who must devise a plan to trap the killer before Janet's time runs out.

A baby is left on Holmes' and Watson's doorstep. The child turns out to be the son of a missing French scientist. When Watson is later brutally attacked and the baby kidnapped, the detectives must find the baby and its father and avoid an international scandal.

"Aunt Lottie", an advice columnist who is actually a man named Alex Doogle, advises a young woman to break up with her violent and insanely jealous boyfriend. The jilted boyfriend then finds Doogle, severely beats him and threatens his life. Doogle turns to Sherlock Holmes, both for his own protection and to save the young woman from her crazed fiancé.

A young boy and his father are traveling on a train, and after they have a fight, the boy runs out of the compartment and seems to have vanished into thin air. Although his governess thinks he has simply run away, Holmes begins to suspect something a bit more serious, and his investigation leads him to a nearby circus.

When a serial killer is sentenced to death, he issues a threat that he will kill Sherlock Holmes before he himself is executed.

Holmes and Watson are called to a boy's school in Belgium. It seems that a young student has gotten into the habit of writing the names of faculty members on the steps of a nearby church, and shortly afterwards person whose name has been written down is found dead.

Sherlock Holmes races against time in order to find the location of a bomb that was planted somewhere in London by an extortionist.

A zealous suffragette acquires a bomb shaped like a croquet ball, intending only to draw attention to her cause, but it is switched with a real croquet ball and explodes, killing a member of Parliament.

When Sherlock Holmes disappears, Dr. Watson and Inspector Lestrade begin a search that leads them to a small shop.

Sherlock Holmes helps Scotland Yard to track down a killer who has been leaving three thistles next to each of the women he has murdered.

Sherlock Holmes helps one of Dr. Watson's old friends by explaining the source of an odd noise in the man's home, but in doing so Holmes uncovers a more serious mystery.

Millicent Channing comes to consult Sherlock Holmes because her fiancé John has disappeared. John has recently been absorbed in his historical study, believing that he has made an important discovery. All that Millicent knows about it is that John was planning to see Sir Thomas Greystone. She tells Holmes about her visit to Greystone Castle, where she was received coldly by the Greystones, and was told that they had never seen John. Holmes proceeds to John's flat to look at his research papers, and he finds a copy of a historical inscription that he then takes with him to Greystone Castle.Millicent Channing comes to consult Sherlock Holmes because her fiancé John has disappeared. John has recently been absorbed in his historical study, believing that he has made an important discovery. All that Millicent knows about it is that John was planning to see Sir Thomas Greystone. She tells Holmes about her visit to Greystone Castle, where she was received coldly by the Greystones, and was told that they had never seen John. Holmes proceeds to John's flat to look at his research papers, and he finds a copy of a historical inscription that he then takes with him to Greystone Castle.

Betty is being tormented by apparent hallucinations, the latest of which she refers to as a 'singing violin'. Her stepfather brings her fiancé to see her in this condition, and he tells the young man that there can be no wedding, because Betty is going to be declared insane. The fiancé goes to consult Sherlock Holmes, but he is murdered before he can see the detective. When Inspector Lestrade consults Holmes about the murder, Holmes recognizes the name of the dead man and also of the step-father, who is the lone surviving partner in a large tea and spice business. Holmes quickly forms a theory about the murder, and sets out to prove it.

Dr. Watson urgently fetches Sherlock Holmes from his club, and brings him to see a French interpreter who urgently needs the detective. The interpreter, M. Dubec, explains how his services were requested by a man named Lattimer, who then abducted him and took him to an unknown location. There Dubec was asked to persuade a Frenchman to sign some papers for Lattimer and an associate, so that they can gain control over his sister's wealth. The case becomes more urgent when the criminals find out about Dubec's meeting with Holmes, and once again take him to their hidden location.

Sherlock Holmes and Dr. Watson return to their flat to find Brian O'Casey waiting for them. The over-excited O'Casey struggles to get his points across, but eventually he explains how he, his friend Albert, and a young woman whom he met in a bakery shop shared the price of a sweepstakes ticket, tearing the ticket into three pieces, one for each of them to hold. Their number won, and they each stand to win 8,000 pounds. But now Albert has disappeared, and unless the other two can find him by midnight, the ticket will expire, and then they won't be able to collect their winnings.

Sherlock Holmes and Dr. Watson are spending a restful day in the country, when they encounter a badly injured man who is carrying an unconscious young woman. They take the pair back to their flat in London, and after Dr. Watson has treated them, the man explains what has happened to them. He is Haterley, a hydraulic engineer with a business of his own. He had been hired by Colonel Stark and an associate, who wanted him to fix a large hydraulic press for them. He was taken to the colonel's country home, where their housekeeper tried frantically to warn him about Stark. After a tumultuous encounter, he and the housekeeper had barely escaped with their lives. From other details, Holmes deduces that Stark was involved in counterfeiting. Holmes, Watson, and Inspector Lestrade then set out to finish the case.

Sherlock Holmes investigates a strange story told to him by a shopkeeper, who claims to have been a member of the 'League of Red-Headed Men' until it unexpectedly dissolved.

Sherlock Holmes tracks down a murderer who uses a young girl to lure victims to empty houses, where they are killed.

Vaudeville escape artist Harry Crocker turns to Sherlock Holmes for help when he is accused of strangling a chorus girl.

The only clue at the site of two grisly murders is a chicken's foot. Baffled, Insp. Lestrade goes to Sherlock Holmes for assistance.

Sherlock Holmes seeks a rational explanation for the Winthrop family legend, which foretells the death of any family member who unexpectedly finds silver coins in his possession.

Dr. Watson accidentally comes home from his club with another man's coat, providing an important clue when the other man is murdered late that same night.

When Dr. Watson thinks that he has seen a ghost, it puts Sherlock Holmes on a trail that leads to a crime at an art museum.

A cowgirl from a visiting rodeo show asks Sherlock Holmes to help her when she discovers a dead man in her hotel room.

Holmes and Watson travel to Sussex to investigate the murder of Squire Douglas, who was shot to death in a sealed-up castle, with only two apparent suspects.

Lady Beryl confesses to a murder that was committed at her home, but Sherlock Holmes is convinced that she is innocent.

Dr. John Watson meets private detective Sherlock Holmes, and assists him in solving a case that has confused Inspector Lestrade.