In the 1920s, Sean Thornton (John Wayne), an Irish-born American from Pittsburgh, travels to his birthplace"Inisfree", Irelandto purchase his family's former farm. Shortly after arriving in Inisfree, he meets and falls in love with the fiery Mary Kate Danaher (Maureen O'Hara), the sister of a bullying but prosperous landowner, Squire "Red" Will Danaher (Victor McLaglen). Will also wants to buy the Thornton family's old cottage and land, and he is angered when the property's current owner, the Widow Tillane (Mildred Natwick), accepts Sean's bid instead of his offer. Will then retaliates by refusing consent for his sister to marry. Soon some village residentsincluding Father Peter Lonergan (Ward Bond) and the local matchmaker Michaeleen Óge Flynn (Barry Fitzgerald)conspire to trick him into believing that the wealthy Widow Tillane wants to marry him, but only if Mary Kate is no longer living in his household. Will now allows Mary Kate to marry Sean; however, at their wedding he realizes he was deceived about the widow's willingness to marry him. He therefore refuses to give his sister her dowry, which consists of 350 Irish pounds in gold, as well as family furniture and other heirlooms Mary Kate inherited from her mother and grandmother.
Sean, unschooled in Irish customs, professes no interest in obtaining the dowry; but to Mary Kate the dowry represents her sense of personal value not only within her family's own history but within the surrounding community as well. She insists that the dowry is hers and must be received to validate their marriage. Angered and shamed by Sean's refusal to confront her brother and demand what is legally hers, she brands him a coward; and, despite living together, they are estranged as husband and wife. Yet, the morning after their wedding, villagers arrive at the couple's cottage with Mary Kate's furniture. The men inform her and Sean that they persuaded Will to release the material portion of the dowry, but they could not convince him to pay the dowry money.
Sean's quiet manner and reluctance to fight for his new wife's dowry are attributed to a tragedy he experienced prior to his return to Ireland. Portrayed in a flashback earlier in the film, scenes depict the event, which occurred during his career as a professional heavyweight boxer in the United States. While fighting as "Trooper Thorn", he accidentally killed an opponent in the ring. Devastated by the death, Sean quit the sport, vowing never to fight again. In Inisfree only one personthe Reverend Cyril Playfair (Arthur Shields)is aware of Sean's former career and the tragedy. The minister many years earlier had been a lightweight boxing champion himself, so he maintains a scrapbook of news articles about the sport. He therefore relates to Thornton's grief and internal conflict regarding the fatal fight.
Early the next morning, in an attempt to force her new husband to confront her brother, Mary Kate quietly leaves their cottage to board a train departing Castletown for Dublin. Sean soon learns from Michaeleen that she has gone to the station, where Thornton finds her and drags her off the train. Followed by a crowd of villagers, he forces her to walk with him the five miles back to the Danaher farm. There Sean confronts Will and demands the dowry money. When he refuses to give it to him, Sean throws Mary Kate back at her brother, declaring "no fortune, no marriage" is their custom, not his. The ultimatum shocks both Mary Kate and Will, who finally pays the 350 pounds, tossing the cash onto the ground. Sean promptly picks up the money and throws it into the fire of a nearby boiler. Mary Kate assists him by opening the boiler's door, an act that shows she never really cared about the money itself, only about what it represents. As the reconciled couple starts to depart for home, Will tries to punch Sean but is knocked down by a counterpunch from his brother-in-law.
A long fistfight ensues between the two men, a battle that attracts more and more spectators as they slug it out across the countryside and into the village. The fighters finally pause for a drink inside Cohan's Bar, where they begrudgingly admit a mutual respect for one another. After arguing over who is to pay for the drinks, Sean ends the fight by hitting Will so hard that he falls back, crashes through the bar's front door, and ends up lying unconscious in the street. Later, with their rift apparently healed, the men get drunk and then together stagger back to Sean and Mary Kate's home for supper.
As part of the story's conclusion, Will and the Widow Tillane begin their own courtship and are shown riding out of the village side by side in a jaunting car carriage driven by Michaeleen. Then, in the film's final scene, Mary Kate and Sean are standing together outside their cottage, smiling and waving, presumably at Michaeleen's passing cart or at some other villagers. Mary Kate then whispers something into Sean's ear, which prompts him to chase her playfully back toward their home.