The rise of Charles Manson and his "family," who are responsible for a series of famous murders in the late 1960s. Manson, a magnetic and mysterious man, attracts road-weary single mother Linda Kasabian to join his collection of outcasts on a ranch outside of Los Angeles. After murdering actress Sharon Tate, Manson and his followers are investigated by district attorney Vincent Bugliosi.

Riggs, a down-on-his-luck screenwriter, struggles to finish a script. But failed suicide attempts, unstable friends, drug deals, and memories of his ex-girlfriend interfere.