The final installment of the Back to the Future trilogy finds Marty digging the trusty DeLorean out of a mineshaft and looking for Doc in the Wild West of 1885. But when their time machine breaks down, the travelers are stranded in a land of spurs. More problems arise when Doc falls for pretty schoolteacher Clara Clayton, and Marty tangles with Buford Tannen.

A new girl comes to the neighbourhood school and Linus is smitten with her. Unfortunately, she develops the symptoms of leukemia and must go to the hospital for cancer treatment. Linus and Charlie Brown help her through the traumas of chemotherapy as best they can while Snoopy plays at being the world's greatest doctor.