At the end of the "Back to the Future", 1985 Doc uses the time machine to travel thirty years in 2015. At the beginning, Doc comes back from the future to 1985 to take 17 year old Marty and his girlfriend Jennifer to 2015 to prevent a disaster with his son Marty Junior. The problem with Marty Jr. is solved, but 17 year old Marty creates another problem that changes events in 1955. They discover this when they go back to 1985. The change in 1955 has turned 1985 into a bad world. Doc and Marty return to 1955 to undo the damage. At the end of the movie, the vehicle is struck by lighting and Doc is sent to 1885.