John Cunningham, a professional assassin with the necessary emotional restraint and life-style, accepts a "hard contract" offer from business associate Ramsey Williams to kill three men in Europe. Upon arriving in Torremolinos, Spain, Cunningham meets socialite divorcée Sheila Metcalf and three of her jet set friends: Adrianne Bedford, an English aristocrat; Maurice, Adrianne's companion; and Alexi, a guilt-ridden ex-Nazi. Sheila learns that Cunningham has sex only with prostitutes. One night she poses as one, spends the night with him, and unexpectedly finds herself emotionally involved. Cunningham carries out the first part of his contract and follows Sheila and her friends to Tangiers to resume their affair. By the time he arrives in Brussels to stalk his second victim, he is beginning to change--his hand is unsteady while committing the murder, and he can no longer find gratification with a prostitute. Matters are further complicated when Ramsey informs him by phone that his final victim is Michael Carlson, a top-notch assassin of 20 years ago, now living peacefully with his family in Madrid. After asking Sheila to join him there, Cunningham accidentally meets Carlson at a Madrid hotel and senses the man's intuitive recognition of what he is. Troubled by this and by Sheila's need to believe that he is something other than a hired assassin, Cunningham is further shaken when Ramsey appears, obviously concerned over a recent telephone conversation with him. Despite his grasp of the situation, Carlson invites everyone to his ranch and, during a philosophical discussion with Cunningham, openly admits that nothing could make him kill again. Torn by his love for Sheila, his obligation to Ramsey, and his compassion for Carlson, Cunningham tries unsuccessfully to return to his emotional void by driving everyone over a cliff as he escapes. At the last moment, however, he is unable to go through with his plan, and disregarding the consequences, he runs away with Sheila.