In Liverpool, Sergeant Jack Truman is assigned to work as a juvenile liaison officer to steer troubled youth away from crime. While investigating minor thefts by young twins Mary and Patrick, Truman meets their older sister, Cathie, and begins a romance with her. However, Cathie's troubled younger brother, Johnnie, leads a local gang and is culpable for a dangerous series of arson attacks. As Truman traces the fires back to Johnnie, the conflict escalates into a tense confrontation and schoolhouse siege.