A crime lab expert and his attractive assistant solve murders, but evidence leads them to their prosecuting friend.
Richard Daniels (Samuel S. Hinds) is elected mayor and tells Gerald Ladimer (Lee Bowman) that Hunter Turnley will be district attorney. Gerald warns Matty (John Litel). Turnley is found murdered, and Gerald announces he will prosecute the murderer. Chemist Jane Mitchell (Marsha Hunt) helps Gordon McKay (Van Heflin) analyze the evidence. Gerald comes in and is interested in Jane. They find a dog hair. Gordon tells Jane he suspects canvas gloves and a burn. They examine people who bought creosote. Allison Stacy resists being arrested and is killed by Captain Lynch (Cliff Clark). Gerald announces his success. Tired of racketeers, in an eating place Eddie Wright (Eddie Quillan) plans to see the mayor at home. Mayor Daniels refuses to see him and calls the police. Daniels asks Gerald how he got $28,000 and says he will investigate him. Matty is paying Gerald $1,000 a week to eliminate his competition and says Gerald must get rid of the mayor. Jane goes out with Gerald, and Gordon is invited to join them.
When Mayor Daniels starts his car, it blows up. Gordon finds a thread. Police arrest Eddie and interrogate him. Gordon says the thread matches Eddie's coat but shows Gerald that his match matches one found at the scene. Men ask Gerald to run for mayor. Gerald has lunch with Jane. Gordon tells her the wire was cut with fingernail clippers. She says she wants to marry, but Gordon mocks the idea. Gordon explains spectroscopic analysis and says 38 magnum powder was used. Jane tells Gerald maybe she will marry him, and he admits he bought 38 cartridges. Gordon checks Gerald's fingernails for powder, and Gerald says that Eddie could have worn gloves. Gordon and Jane suction suspects' hair for powder and burlap. Gordon finds a pencil impression that the mayor was going to investigate Gerald. Gordon calls him to come over and spills something so he can vacuum Gerald's hair. Gordon tells Jane that he solved the case but won't say who it is yet. Gerald and Jane plan to go away, and she says how Gordon found the murderer. Gerald calls Matty to come over and has Jane take his car. Gerald tells Matty that Gordon has him, and Matty gives Gerald a pistol. Jane checks a clipper on Gerald's key-ring and sees it matches. Gerald comes in with a gun and demands Gordon's evidence. They fight, and police arrest Gerald. Six weeks later Jane comes back, and Gordon asks her to marry.
This scientific crime investigation using forensic evidence
pioneered a new genre, intriguing and reassuring people that modern
science can help catch criminals and convict them with objective
proof. The friendly working relationship between Gordon and Jane
resulted in natural love.