An Irish lass is branded a traitor when she falls for a British soldier.

In an Irish seaside town in 1916, Rosy Ryan, daughter of tavern owner Tom Ryan, accepts the marriage proposal of her former schoolteacher, widower Charles Shaughnessy. After the marriage, Rosy quickly realizes that Charles lacks interest in sex, and she goes to talk with Father Collins, who reprimands her and tries to convince her that she is a lucky woman to have such a good man for a husband. Maj. Randolph Doryan, a shell-shocked British soldier, arrives in town to help control contact between the Irish Republican Army and the Germans, and soon Rosy and the young soldier fall in love. They make love in the meadow outside of town, and Michael, the town idiot, finds a button torn from Randolph's clothing and walks through the town displaying the evidence. The townspeople begin to gossip, but the talk does not affect Charles, who is confident that the romance will weaken by itself. When IRA leader Tim O'Leary arrives seeking aid to retrieve munitions from the offshore ruins of a German ship, Tom Ryan, fearful of reprisals, informs on O'Leary, and the British soldiers quickly arrest him. The townspeople, however, believe Rosy to be the traitor because of her relationship with Randolph and descend on Charles's house, strip her, and cut off her hair, while Charles and Tom helplessly watch. Randolph, realizing that he has lost Rosy, shoots himself. Rosy, meanwhile, decides to leave town with Charles, who is willing to try and start a new life in Dublin.