The story is narrated by Sherlock Holmes and recounts an early case from his time as a student. An old schoolmate of Holmes, Victor Trevor, visits him and tells him the story of his father's past.
Victor's father, Mr. Trevor, had been a successful businessman who was involved in a dark secret from his younger days. As a young man, Mr. Trevor had been part of a group of friends aboard a ship called the Gloria Scott. During the voyage, the friends mutinied and killed the captain and crew. Mr. Trevor was forced to go along with the mutiny under threat of death.
After the mutiny, the group went their separate ways, but the guilt haunted Mr. Trevor for the rest of his life. When an anonymous note arrives revealing the old secret, Mr. Trevor dies from the shock. Sherlock uses the limited information to deduce the identity of the blackmailer and bring the case to a close. The story provides an early glimpse into Sherlock's remarkable deductive abilities.