Jonas Wilde, a British secret service agent licensed to kill, returns from a successful mission determined to resign. Canning, his London superior, agrees to forward his resignation if Wilde eliminates a Czechoslovakian scientist defector now being held by the Americans. With the help of a housekeeper, Rhoda Gooderich, Wilde kills the scientist but is himself captured and interrogated by CIA agent Lucinda. After Lucinda tells Wilde that someone in his organization is causing fellow British agents to be killed by mistake, Wilde escapes to look for Canning, who mysteriously has disappeared. Accompanied by Canning's wife, Barbara, Wilde heads for the leader's base in the Channel Islands and learns from Stern, a fellow agent, that still another member of their unit, Peter Ravenspur, has been murdered. Wilde and Stern then take Mari, who has claimed to be Ravenspur's niece, aboard Stern's boat for questioning. Stern then exposes himself as the double agent and is killed by Wilde. Mari, who has actually been working for Lucinda, is killed by a stray bullet, while Wilde escapes. Back in London, he kills his girl friend, Jocelyn, after realizing that she has been working for Stern. Leaving Jocelyn's flat, Wilde runs into Canning, who explains to him that he is too valuable an agent to be allowed to resign and advises him to go under cover until he is again needed.