Bowman and Thornton, the heads of competitive protection agencies, and police chief Tinley have been close friends since childhood. Unknown to both Tinley and Thornton, however, Bowman has been hiring thugs to rob shipments protected by Thornton and other agencies in order to wipe out his competition. After a policeman is killed in one of Bowman's hold-ups, Tinley's son Bob, a junior officer, becomes determined to destroy the gang. When Bob, who is engaged to Bowman's daughter Gail, sees convicted robber Dugan leaving Bowman's office one day, he immediately becomes suspicious, but is assured by his father that his old friend is honest. Acting on a tip, Bob tracks Dugan to an apartment building, but is knocked out by Dugan's henchmen before he can catch him. Later, Bob visits Moran, a retired policeman and an expert on the local robbery scene. Moran confirms Bob's hunch that Dugan is behind the hold-ups, then decodes a message that is being broadcast on the radio by a drummer who is in cahoots with Dugan. According to the message, the leader of the gang will dine at a certain Mexican restaurant that night. Although Bob and his partner, Corrigan, are startled to see only Bowman at the restaurant, Moran assures Bob that the message was accurate. While Bob tries to bring in some of Dugan's thugs, Bowman, desperate for cash, arranges with Dugan to hold up a bank shipment that is being protected by one of his own trucks. Tinley assigns Bob to guard the shipment, and Gail insists on accompanying him. When Bowman hears that his daughter is with Bob, he telephones Tinley in a panic and warns him that the shipment is to be robbed. Tinley immediately dispatches more policemen to the scene, but Bob manages to chase and apprehend Dugan by himself. As he is arrested, Dugan implicates Bowman in the crimes, but Bowman commits suicide before he can be questioned. After learning of his friend's death, Tinley insists that Gail be told that Bowman died accidentally, and Bob gladly tells Gail that her father died while fighting the gang.
