Time-traveling is just too dangerous. Better that I devote myself to study the other great mystery of the universe: women!

　　 Ah yes, Marty and Doc, two old friends.

　　 The second part of the Back To The Future trilogy finds Marty (Michael J. Fox) and Doc Brown (Christopher Lloyd) headed to 2015 to help out Marty and Jennifer (Elisabeth Shue)'s kids. While they're in the future, an older version of Biff takes the time machine and goes back to 1955 to give young Biff a book: a sports almanac that will let him correctly predict every sporting event for the next 30 years, allowing him to make his fortune. Marty and Doc return to an alternate 1985,where Biff's in charge and Marty's dad is dead and Doc's been committed. They then have to go back to 1955 and change things again, all while not being seen by the 1955/1985 versions of themselves already in 1955, and not changing anything that they've done in 1955.

　　 Got all that?