- Saturday, October 26
- 9:00 p.m. Marty, Doc, Jennifer and Einstein arrive from 2015 in Timeline 9 back in 1985. After bringing Jennifer back home, Marty is dropped off at his house by Doc, who returns to his lab with the intention of dismantling the DeLorean. However, Marty discovers that an African-American family now resides within his house and is chased out by them. Running through the streets, Marty runs towards to a house, picks up a newspaper and discovers that he is, in fact, in 1985. The house's owner, former principal Stanford S. Strickland, holds Marty at gunpoint with a pump-action shotgun. However, a group of drive-by shooters drive by and open fire on the house, distracting Strickland and allowing Marty to run away towards downtown.
- Realizing that time had been altered, Doc breaks into the Hill Valley Public Library in order to discover what had gone wrong. Upon discovering that, in this timeline, he had been committed to the County Asylum, Doc disguises himself and travels to the asylum where, posing as his counterpart's distant cousin, Mr. Von Braun, he bribes the asylum nurse to talk with his alternate self. He discovers that, at some point after being committed, his counterpart had been lobotomized.
- Walking through downtown and bumping into Red the Bum, Marty subsequently discovers that the Hill Valley Courthouse had been turned into Biff Tannen's Pleasure Paradise Casino & Hotel. Entering the Biff Tannen Museum, Marty discovers that, in this timeline, Biff and Lorraine had gotten married in 1973, much to his horror. Afterwards, Marty is apprehended by Biff's gang, who are now serving as Biff's bodyguards, who knock him out.
- Upon waking up at the 27th floor, Marty discovers that Lorraine had gotten breast implants and that Biff is angry at him for not being at his boarding school in Switzerland. After witnessing Lorraine and Biff's argument, in which Biff managed to force her to stay by threatening to cut off not only her, but her children as well, Marty asks Lorraine about the whereabouts of his father, George McFly. This prompts Lorraine to reveal that George had died in 1973 and was buried at Oak Park Cemetery.
- Making way to George's grave, Marty is sorrowful upon finding it. Shortly after, Doc finds Marty, having learned about George's death as well. At Doc's garage, Doc explains that the timeline had been altered and reveals that he had found the top of old Biff's cane as well as a Blast from the Past bag containing the receipt for Grays Sports Almanac. Realizing that old Biff had gone back in time and given the almanac to his younger self, Marty decides to go ask Biff how he had obtained.
- Sunday, October 27
- Making his way back to Biff's penthouse on the 27th floor of the casino-hotel, Marty confronts Biff and asks him about the almanac. In his office, Biff shows Marty the almanac and reveals that he had received it on November 12, 1955, much to Marty surprise. However, unaware that the old man was his future self, Biff also reveals that the old man who gave it to him had also warned him that some day a "crazy wild-eyed scientist" or "a kid" might show up asking about that book and that Biff had to get rid of them if that ever happened. Fortunately, Marty manages to distract Biff and, dodging Biff's shots, runs towards the hallway. However, Biff's gang emerge from the elevator and start pursueing him, but Marty manages to trick them by jumping over to another flight of stairs. While they run downstairs, Marty climbes back up and goes to the roof instead.
- On the roof, Marty is confronted at gunpoint by Biff, who remarks that he owns the police and reveals that he had used the same gun to kill George. Fortunately, as Biff takes aim, Marty jumps from the roof on top of the DeLorean, which then hovers into view. Biff is knocked out by being hit on the jaw by the gullwing door when it is opened by Doc, allowing Marty to get inside the car.
- 2:42 a.m. Marty informs Doc about the date on which old Biff gave his younger self the almanac, much to Doc's astonishment. Doc assures Marty that once they succeed in their mission, the alternate 1985 will change back into the real 1985, instantaneously transforming around Jennifer and Einstein, leaving them with no memory of the alternate timeline. Marty and Doc then depart to 1955. This creates Timeline 11, which begins at Marty and Doc entry point in 1955 and Timeline 10 fades away.
- Saturday, October 26
- Back to the Future trilogy
- Back to the Future (IDW Publishing)