Marty McFly (Michael J. Fox) finds Doc Brown (Christopher Lloyd) in 1885 after receiving a letter from him, but upon arrival, they discover that Doc is in danger from Biff's great-grandfather Buford "Mad Dog" Tannen. Marty rescues Doc and then returns to 1985 with the help of a steam locomotive, which uses a rail spur line to reach 88 miles per hour and time-travel. Along the way, Doc falls in love with schoolteacher Clara Clayton, but eventually ends their relationship to return to his own time.