Adapted from Daphne Du Maurier's novel, a young woman discovers her aunt is surrounded by pirates preying on wrecked ships for the local judge.
On the stormy Cornish coast a ship wrecks. Pirates kill the crew and steal the goods. Mary (Maureen O'Hara) is let out of a coach near the feared Jamaica Inn. Sir Humphrey Pengallan (Charles Laughton) at a dinner party offers her a horse to ride there and takes her trunk for her. Mary is welcomed by her aunt Patience (Marie Ney) and her rough husband Joss Merlin (Leslie Banks). The gang complains to Joss that the last haul did not pay enough. Patience tells Joss that Mary came with Humphrey, who gives Joss orders. Jem Trehearne (Robert Newton) is caught with money. Joss and Humphrey order him hanged. From above Mary sees it and cuts the rope. She rescues Trehearne. Patience tells Mary to go. Mary hides with Trehearne, and they escape to a shore cave. Mary tries to leave in the rowboat; but he stops her, and the boat is lost. The gang finds them; but they swim away.
Humphrey judges individuals at home. Mary and Trehearne come to him for help. Trehearne shows Judge Humphrey he is an officer of the law and says wrecks there have no survivors. Trehearne says the leader is Joss, but they must find his boss. Humphrey has Trehearne write a letter, and Mary overhears. She took the coach and warns Patience. Trehearne and Humphrey arrive with pistols and arrest Joss; but Humphrey tells Joss a ship is carrying gold while Trehearne locks Mary and Patience in a bedroom. Trehearne asks Joss to name his boss. The gang arrives and captures Trehearne and Humphrey. Joss has Trehearne and Humphrey tied to chairs and asks Patience to watch them while they go to the wreck with Mary. Humphrey is not tied and tells Patience to watch Trehearne, who pleads with her. Mary uses a lamp and raises a burning flag to warn the ship. Harry (Emlyn Williams) rips her dress and shoots Joss as he and Mary escape on a cart.
Humphrey says good-bye to his butler (Horace Hodges) and leaves in his coach. Mary takes wounded Joss to Patience, who knows who the boss is but is shot by Humphrey. Joss dies too. Humphrey gags and ties Mary to take her with him. Harry and the gang return. Before they scatter, Trehearne and soldiers arrest them. Trehearne and the soldiers follow Humphrey, who takes Mary on a ship. Humphrey ungags Mary, and she screams. Trehearne catches Humphrey, who climbs the rigging and jumps to his death. In the final shot his aristocratic friend is horrified.
This under-rated Hitchcock film exposes early 19th century
piracy and the greedy judge who leads the cut-throats. Courageous
Mary and Trehearne manage to catch the criminals who murder witnesses
so they won't hang.