As the wind whips the Cornish Coast, a band of cutthroats scuttle ships unlucky enough to sail past the Jamaica Inn. Into this air of foreboding comes Mary, looking for her aunt Patience, the sister of her dead mother. Stranded on the road to the inn, Mary meets Sir Humphrey Pengallan, a half-mad squire who is so taken with her beauty that he offers to accompany her to the inn. Once there, Mary is greeted by a leering bully of a man, who turns out to be her uncle, Merlyn Joss. Joss is the leader of the pirates, but secretly, Sir Humphrey is the real brains of the operation, and he orders Joss to allow Mary to stay. That night, Mary watches in horror as the pirates prepare to hang Jem Trehearne, whom they suspect of pilfering their booty. As the men fight over Trehearne's shoe buckles, Mary cuts the rope, and the two fugitives flee into the night. Unwittingly, they turn to the squire for help. Trehearne confides that he is an undercover police officer investigating the wrecks off the coast. The squire tricks Trehearne into returning to the inn with him, and Mary, overhearing the confession, rides to warn her aunt. While the squire and Trehearne await the arrival of the mastermind, the scuttlers appear and take them prisoner. After the men leave to scuttle another ship, Trehearne is shocked as Sir Humphrey unties his own bonds and orders Patience to stand guard over Trehearne. After the squire departs, Trehearne strikes a bargain with Patience: his freedom for that of her husband. Trehearne then rides for help as Mary attempts to warn the unsuspecting ship. Enraged, the men shoot Joss as he tries to protect Mary from their wrath. She then manages to return to the inn, where she is kidnapped by the crazed squire, who carries her off to his ship. Returning with the troops in the nick of time, Trehearne captures the scuttlers and rescues Mary as the squire leaps to his death.