In Back to the Future Part II, the alternate 1985 is a dark, twisted version of the normal year created when Biff Tannen uses a sports almanac from the future to get rich and powerful. This nightmare world shows what happens when one selfish act ripples through time to ruin everything.
The story starts when Marty McFly and Doc Brown go to 2015 to save Marty’s future son from jail. While they are away, old Biff overhears their plan and steals the DeLorean time machine. He flies back to 1955 and gives his younger self the almanac, which lists every sports winner from 1950 to 2000. Young Biff uses it to bet on games and horses, turning himself into a billionaire casino owner almost overnight.https://en.wikipedia.org/wiki/Back_to_the_Future_Part_II
When Marty and Doc return to what should be their 1985, they find a hellscape instead. Hill Valley is a slum covered in graffiti and decay. Biff’s towering casino hotel dominates the town, complete with a giant gold statue of himself. Police cars chase people through the streets, and the courthouse is a wreck. Marty’s family has fallen apart. His father, George, is dead, killed by Biff. His mother, Lorraine, is an unhappy, overweight alcoholic married to Biff. His siblings, Dave and Linda, are losers living in the garage, scraping by on dead-end jobs.https://en.wikipedia.org/wiki/Back_to_the_Future_Part_II
Marty sneaks into Biff’s penthouse suite at the casino. There, he sees a newspaper clipping about George’s murder and watches a video of Biff bragging about killing him. Biff even shows off the sports almanac, now worn from years of use. This version of Doc Brown is locked up in a mental hospital, labeled insane for talking about time travel. Biff tries to murder Marty by throwing him off the building, but Marty escapes.https://en.wikipedia.org/wiki/Back_to_the_Future_Part_II
Doc figures out the problem fast. Biff got the almanac on November 12, 1955, right after Doc hid it in the DeLorean. They steal the almanac back from 1955 Biff and burn it in the parking lot of the Enchantment Under the Sea dance. As the flames destroy the book, the timeline snaps back to normal. The bad 1985 vanishes, replaced by the better world from the first movie where George stands up to Biff.https://en.wikipedia.org/wiki/Back_to_the_Future_Part_II
This alternate 1985 drives home the movies’ big idea about choices and timelines. One change in the past, like handing over that almanac, poisons the future for everyone. It makes the normal 1985 look like paradise by comparison.
Sources
https://en.wikipedia.org/wiki/Back_to_the_Future_Part_II
https://www.youtube.com/watch?v=778UvZ_Ccak
https://collider.com/back-to-the-future-3-divisive-film-revisit/
