 When FBI Agent Zack Stewart (Kenneth Tobey) is killed, Agent John Ripley (Broderick Crawford) takes over the three cases he was working on, hoping one will lead to his killer. The first involves gangster Joe Walpo (Joe Bassert) and Ripley finds his hideout through Joe s girl friend, Connie Anderson (Martha Hyer). Joe is killed but it is established he was 400 miles away when Stewart was murdered. The next involves a car-theft gang which Ripley breaks up by using one of the gang, Vince Angelino (Gene Reynolds) and his wife Julie (Marissa Pavan.) The last case involves Kate Martel (Ruth Roman), the victim of an extortionist who threatens to kidnap her child unless she pays him $10,000.