Detective Sergeant Walter Brown (Charles McGraw) of the Los Angeles Police Department and his partner are assigned to protect a mob boss's widow, Mrs. Frankie Neall (Marie Windsor), as she rides a train from Chicago to Los Angeles to testify before a grand jury. She is also carrying a payoff list that belonged to her murdered husband. On the way to pick her up, Brown bets his partner and friend, Sergeant Gus Forbes (Don Beddoe), what she will be like: "She's the sixty-cent special. Cheap. Flashy. Strictly poison under the gravy."