Based on the novel by Liam O'Flaherty and winner of Academy Awards for direction, screenplay, actor, and musical score, a poor Dubliner informs on his friend for twenty pounds and is executed by the Irish Republican Army.
In 1922 Dublin Gypo Nolan (Victor McLaglen) looks at a reward poster for Frankie McPhillip and tears it down. When he sees his girlfriend Katie (Margot Grahame) prostituting herself on the street for rent money, he jealously knocks the man down. She points out that they could go to America for ten pounds each. Frankie McPhillip (Wallace Ford) hides from the police and sits by Gypo in a restaurant, asking about his mother. Gypo says he has been court-martialed by Sinn Fein; now he fears both the British and the Irish, who suspect him. Gypo goes to the police station for the reward. Frankie goes home to his mother (Una O'Connor) and his sister Mary (Heather Angel). The police break in. Frankie shoots a policeman and is killed.
Gypo is given twenty pounds reward and buys whiskey, hearing Frankie's voice saying he is lost without him. Katie apologizes to Gypo, who says he robbed an American sailor. Gypo gives a pound to a blind man. He goes to the McPhillip wake, says he is sorry, and drops coins. They say they do not suspect him, and he hurries away. Dan Gallagher (Preston Foster) burns the wanted poster and offers to reinstate Gypo if he will find the informer. Gypo says he has been poor for six months and drinks. He accuses Mulligan, saying Frankie got his sister in trouble. Dan says a court of inquiry will meet at one a.m. Bartly (Joe Sawyer) says it was Gypo.
Gypo gets even drunker, knocking out a man and a policeman. Men call him king, and he buys them fish and chips. Gypo visualizes going to America with Katie. Gypo goes to a fancy party and buys drinks for all. At the wake Mary sees Dan and kisses him. Dan says that an informer could wipe out the organization. Mary tells him that Frankie said he had to see Gypo. Gypo gives a woman five pounds fare to London and another woman four pounds for food and lodging. Bartly gets him to go to the meeting at one. Katie asks Gypo why he didn't come. Gypo tells her he got 20 pounds for her.
At the inquiry Gypo is drunk and tells sick Mulligan (Donald Meek) he should be in bed. Seeing the court, Gypo accuses Mulligan. Dan asks Mulligan where he was since noon, and his story is corroborated. Dan asks Gypo, who admits he saw Frankie. Dan asks Gypo who was the informer. Gypo says he doesn't know why he did it. Men draw straws, and Dennis has to do it. The strong Gypo escapes through the roof amid shooting. Dan says the movement is finished if he gets away. Gypo goes to Katie and tells her he informed, laying down by the fire. Katie goes to Dan and begs for Gypo, saying he didn't know, but telling him where he is. Dan says the court judged him. Dennis and two others break in on Gypo. He escapes but is shot by Bartly. Gypo staggers into a church and confesses to Frankie's mother, who forgives him for not knowing what he was doing. Gypo calls out to Frankie that his mother forgave him and dies.
This poignant study of the pressures on a poor man in an underground movement fighting for their rights and survival portrays the moral weakness and lack of awareness in a physically strong man.