Eighties teenager Marty McFly is accidentally sent back in time to 1955, inadvertently disrupting his parents' first meeting and attracting his mother's romantic interest. Marty must repair the damage to history by rekindling his parents' romance and - with the help of his eccentric inventor friend Doc Brown - return to 1985.

Hoping to alter the events of the past, a 19th century inventor instead travels 800,000 years into the future, where he finds mankind divided into two warring races.