In advance of a presidential visit to the small town of Suddenly, California, a trio of FBI agents enter the Benson family's home to assess potential security risks. Once inside, leader John Baron (Frank Sinatra) reveals himself as a psychopathic assassin, and he kidnaps the family in order to use their house as his vantage point in his plot to kill the president. Sheriff Tod Shaw (Sterling Hayden) matches wits with the assassin and his gang in an attempt to save the day.