On an autumn night on the coast of County Mayo, Ireland, a young woman named Pegeen sits alone in the pub owned by her father, Michael Flaherty. Pegeen’s fiancé, Shawn, comes to see Pegeen and mentions hearing a man groaning in a ditch. Michael and his friends Jimmy and Philly stop by the pub on their way to a wake, where they will spend the night. Michael, Jimmy, and Philly try to intimidate Shawn to spend the night with Pegeen, who fears being alone in the pub at night, but because Shawn doesn’t want to upset Father Reilly, he refuses and runs out of the pub. He returns soon after, afraid that the man he heard groaning is now following him. The man from the ditch, Christy Mahon, comes into the pub and reveals that he is on the run from the law after killing his father by hitting him with a loy while working in the potato field.

Impressed by Christy’s story, Michael offers him the position of “pot-boy” at the pub, which Christy accepts. After Shawn, Michael, Jimmy, and Philly leave, Christy and Pegeen are left alone. Christy tells Pegeen more about his life working on his father’s farm and his father’s cruel nature, and the two begin to form an attraction. They are interrupted when Widow Quin, a local woman known to have killed her husband, knocks at the door. Widow Quin says she has instructions from Shawn to let Christy spend the night at her house instead of the pub, but Pegeen demands that Christy sleep at the pub as that’s his job as pot-boy. The next morning, some girls from the village, along with Widow Quin, come to the pub to see Christy. Christy dramatically recounts for them the story of how he killed his father. When Pegeen arrives and sees the attention the other women are paying Christy, she becomes jealous and orders them out of the pub. Pegeen warns Christy to be careful of whom he tells his story to, as the village girls may tell the local police of his crime and whereabouts.

Shawn and Widow Quin come to the pub to talk to Christy. After distracting Pegeen, Shawn offers to give Christy a ticket to the United States as well as his new, fine clothes if Christy will leave the village for good. Christy takes the clothes from Shawn but refuses to leave. After Christy leaves the room, Shawn laments the idea of losing Pegeen to Christy. Widow Quin then offers to marry Christy so that Pegeen cannot marry him, to which Shawn happily agrees. After Shawn leaves the pub, Christy goes to show off his new clothes to Pegeen. However, he reels back when he sees his father, Old Mahon, clearly wounded but not dead, approaching the pub. Christy hides behind the door as Old Mahon asks Widow Quin if she has seen his son, whom he describes as a liar and a lazy fool. Widow Quin sends Old Mahon in the wrong direction, and after Old Mahon leaves, Christy pleads with Widow Quin to swear that she will not tell Pegeen that his father is still alive. Widow Quin agrees in exchange for Christy giving her supplies from the pub once he has married Pegeen.

Later that afternoon, Jimmy and Philly are at the pub discussing Christy’s impressive performance in the village sporting events as well as how much he brags about killing his father. Old Mahon enters the pub and listens to their conversation, coming to understand that Christy has been there. Widow Quin covers for Christy by telling Philly and Jimmy that Old Mahon is a lunatic. Old Mahon looks out the window at the sporting event and recognizes Christy, but Widow Quin convinces him that the man he sees is not his son. Old Mahon believes Widow Quin as he cannot fathom that his Christy would be so beloved by the people in the village. Old Mahon leaves the pub. Later, Christy and Pegeen enter the pub, and Christy describes in detail the future he and Pegeen can have together, convincing Pegeen to agree to marry him. Michael arrives with Shawn, and Pegeen tells both men that she plans to marry Christy. Michael is at first horrified by the thought of Pegeen marrying a murderer, but when Shawn refuses to fight Christy and leaves, Michael gives his blessing for Christy and Pegeen to wed.

Old Mahon enters the pub followed by the villagers, announces that he is Christy’s father, and begins beating Christy. Christy tries to convince Pegeen that Old Mahon is insane, but the crowd and Pegeen do not believe him. Christy picks up a loy and chases Old Mahon out of the pub, hitting him with what he thinks is a fatal blow. Christy believes that Pegeen and the other villagers will be as impressed by him now as they were when they first heard his story, but they worry about attracting attention from the police to their community. The crowd decides to deliver Christy to the police. Shawn and Pegeen tie a rope around Christy and begin to drag him outside when Old Mahon, who is still alive, crawls back into the pub. Old Mahon frees Christy from the ropes and says he and Christy will be leaving but they will tell others of the wickedness of the people in Mayo. A defiant Christy declares he’ll leave, but going forward, he will be the captain and his father the “heathen slave.” After they leave, Shawn turns to Pegeen to discuss their wedding. Pegeen hits Shawn on the head and cries that she has lost “the only Playboy of the Western World.”