The members of an unnamed political group discuss their plans to pursue their goals by peaceful means. Unfortunately, their opponents do not feel the same way and attack the meeting. A shoot-out ensues and several members of the group, including Katie, the only female, narrowly avoid being shot. The attackers are eventually fended off, but as the party members regroup a man enters the building. Katie's boyfriend, Francis McPhilip, instinctively fires at the man. The party leader Gallagher goes to examine the body and Francis' terrible mistake is revealed - he has killed the Chief of Police.

To preserve its tenuous political position, the party publicly disowns Francis and provides him with money to leave the country. The night before he leaves he risks being caught and ventures into the city to say goodbye to his mother. He attracts the attention of a policeman and goes to Katie's flat to hide. He asks her to come away with him, but she reveals that she is now seeing his best friend, Gypo Nolan. When Gypo returns, Katie tries to slip Francis out, but Gypo spots him. He confronts Katie, who becomes angry that Gypo does not trust her. She tells him she is leaving with Francis and Gypo storms out. Katie goes to warn Francis, but as the former lovers bid farewell they are seen by Gypo. Believing that Katie is going to elope with Francis, Gypo goes to the police station seeking revenge. He informs the officer on duty of Francis's whereabouts and reluctantly takes the reward money that is offered.

The police arrive to arrest Francis and chase him to the roof, where he falls to his death. Gypo, who has gone to drown his sorrows, hears the news and regrets his hasty action. He bumps into Katie, who tells him she was never going to leave him but was merely angry that Gypo did not trust her. Realising that his betrayal of his friend was for nothing, Gypo confesses what he has done and tells Katie that Francis is dead. Although shocked, Katie tells Gypo she still loves him and will help him. Gallagher discovers that a man fitting Gypo's description was the police informer. He asks Gypo, who denies it, and then sends him to offer the party's condolences to Francis' grieving mother. Gallagher's men follow him and see him accidentally drop the reward money. They realise he is guilty, but Gypo runs away.

When the other gang members return to Katie and Gallagher, Katie pretends she did not know that Gypo was the informer. In private, she attempts to persuade Gallagher to let Gypo escape but he refuses and he and his men begin to hunt Gypo down. At the train station, Gypo gives up his chance to get away by giving his money to a needy young woman. Before taking the train she gives him a signed photograph of herself. Gypo leaves the station and is captured by the gang. Once again he manages to escape. He runs into a tunnel and his pursuers believe that he has been killed by an approaching train.

Gypo is not dead, however, and returns exhausted and bleeding to Katie. She tells him she is going to the police to ask for protection but on her way out meets Gallagher, who has come to tell her of Gypo's death. He shows her the photo the young woman gave Gypo and tells her that she is better off without him. Feeling betrayed, Katie tells Gallagher that Gypo is not dead and is hiding in her flat. He goes to get the other men and Katie waits with her lover. Gypo asks her if she thinks God will forgive him and says that helping the woman at the station made him feel better. Katie realises her mistake and admits what she has done. Gypo forgives her and leaves to face the party members. They shoot him and he manages to stagger to a nearby church and ask Francis's mother for forgiveness before collapsing on the floor of the church.