In this final chapter, Marty McFly (Michael J. Fox) obtains a 70-year-old message from the time-traveling Dr. Emmett Brown (Christopher Lloyd), in which he informs Marty that he has retired to a small town in the Old West. Marty then finds out that the Doc was murdered shortly after sending the letter. In order to save his friend, Marty will have to travel back in time, disentangle a lovestruck Doc from a local schoolmarm, and repair the DeLorean -- all while avoiding a posse of gunslingers.