John Cunningham (James Coburn) is a cold-blooded assassin sent by his superior Ramsey (Burgess Meredith) to murder three people in Europe. He takes off for Spain where he meets a foursome of jet-setting socialites. Sheila (Lee Remick) is a wealthy divorcee who falls for John. Alexi (Patrick Magee) is a former Nazi weasel who has eyes for Sheila. Adrianne (Lilli Palmer) is a social butterfly who plays Cupid for John and Sheila. Sterling Hayden and Claude Dauphin also star in this romantic story of how love can soften a man's stone-cold heart.