A young teenager named Mikey Walsh finds an old treasure map in his father's attic. Hoping to save their homes from demolition, Mikey and his friends Data Wang, Chunk Cohen, and Mouth Devereaux run off on a big quest to find the secret stash of Pirate One-Eyed Willie.

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.