Back to the Future. Part II

This movie picks up where the last one left off; with Doc Brown and Marty going into the future to help Marty's future offspring. After doing that they returned to their own time, only to discover that things have changed. They discovered that while in the future, Marty's nemesis, Biff Tannen got the sports book that Marty bought so that he could know the results of sports events and make a killing, but Doc Brown nixed his plans, but Tannen who overheard their conversation, got the book and the time machine and went back into the past and gave the book to himself, who has not only amassed a fortune but also extremely powerful. So Doc and Marty have to go back to when Biff got the book and get it away from him. And it seems that it was in 1955 on the night of the dance that Biff got the book. So not only must they get the book but they must also avoid the other versions of themselves.