Jin Vaus, Jr., U.S. Army electronics expert, is sentenced to a stockade term for unauthorized use of government equipment. He keeps it a secret from his fianc?(C)e, Alice, and pretends he has been overseas when he is discharged, and they are married.. He opens an electrical engineering company and becomes involved with a gangster mob headed by Charles Rumsden. She begs him to quit but he is useful to the crooks, discovering wiretaps, setting up alarm systems and even saving a hoodlum's life by disconnecting a time bomb. Gang-member Tony urges Jim to invent a device that could tap lines carrying race results and delay them so they could make some big money on post-race betting. After Tony is killed by a fellow mobster, Alice persuades Jim to attend a tent meeting held by evangelist Billy Graham. Graham's sermon and words so inspire Jim that he gives up his criminal activities.