Dimo and Veska, members of a combat group made by the young people, get acquainted at the secret meeting. The group's first operation fails: the bomb placed in the theatre does not go off. Owning to Dimo, the second assignment goes wrong. He is suspecting of being a traitor. The leader of the group, Mladen, narrowly escapes an ambush. After a discussion, the group decides to isolate Dimo. Veska, who is in love with him, has faith in him. The traitor is Slavcho, a former colleague of Veska and now police agent. He keeps calling on Veska and spies on the young people. He visits Dimo's neighbor Tzveta several times too. Confined to a wheelchair, Tzveta goes in for photography. From her negatives, the agent learns of Mladen's visits to Dimo. The questions he asks her make it clear to Tzveta that Slavcho works for police. She tries to warn Dimo, but on the way her wheelchair goes out of control, she crashes into tree and dies. Dimo is arrested.