Sherlock Holmes meets with Mr. Jabez Wilson, a pawnbroker, who presents a strange case involving the Red-Headed League.

• Holmes infers Wilson's background as a Freemason, laborer, visitor to China, and a recent writer.
• Wilson describes joining the Red-Headed League after responding to an odd advertisement.

Wilson recounts his peculiar experience with the Red-Headed League, which required him to transcribe the encyclopedia for a high wage.

• Wilson was selected for his vibrant red hair and given a well-paid job copying the encyclopedia.
• His assistant, Vincent Spaulding, encouraged him to apply and was instrumental in Wilson's involvement.

The sudden disbandment of the Red-Headed League leads Wilson to seek Sherlock Holmes' assistance.

• After two months, Wilson finds the League disbanded and the mysterious interviewer, Duncan Ross, gone.
• Holmes takes on the case, intrigued by its remarkable nature.

Sherlock Holmes begins his investigation by visiting Wilson's pawnshop and examining the surrounding area.

• Holmes meets Wilson's assistant, Vincent Spaulding, and conducts a brief interview.
• He then examines Wilson's place of business and the nearby streets.

Holmes uncovers the true nature of the Red-Headed League and invites Watson to join him in stopping a significant crime.

• Holmes asks Watson to meet him later that night to prevent a considerable crime.
• Watson is left in suspense, wondering about the nature of the crime and the criminal.

Holmes and Watson join forces with a bank director and a police officer to thwart a bank robbery.

• Sherlock reveals that a planned bank robbery is the crime they are there to prevent.
• The group hides in the bank vault awaiting the robbers.

The criminals are caught in the act of robbing the bank, and Sherlock Holmes explains their elaborate scheme.

• Holmes and company capture Wilson's assistant Spaulding and his accomplice, both revealed to be the thieves.
• The Red-Headed League was a front to keep Wilson busy while the thieves tunneled into the bank.

Holmes concludes the case by explaining the motivations behind the Red-Headed League and the true identity of the criminals.

• Spaulding, revealed as the notorious thief John Clay, masterminded the plot for his own gain.
• Holmes ties the pieces together, revealing how he deduced the plan.