- Wednesday, October 21
- Doc, Marty and Jennifer arrive from 1985. In order to prevent Jennifer from discovering too much about her and Marty's future, Doc knocks her out with a Sleep-inducing alpha rhythm generator.
- Upon landing, Doc instructs Marty to change his clothes to ones resembling those of his future son, Marty Jr., whom Doc explains was going to be arrested for attempted robbery of the Hill Valley Payroll Substation early the next day and tried, convicted and sentenced to fifteen years at the State Penitentiary within two hours of his arrest. After they move the unconscious Jennifer out of the DeLorean, Doc instructs Marty to go to the Cafe 80's and refuse Griff's offer while Doc himself goes to intercept the real Marty Jr.
- In the Cafe 80's, Marty is confronted by an elderly Biff Tannen, who remarks on how Marty Sr. had flushed his life completely down the toilet. However, their conversation is interrupted by Griff, Biff's grandson, who instructs Marty to stay inside while he starts argueing with his grandfather outside. However, the real Marty Jr. shows up shortly afterward, having woken up earlier due to Doc's sleep-inducer not having enough power due to its recent use on Jennifer.
- After Griff throws Marty Jr. over the counter, Marty takes his place and stands up to Griff, refusing his offer. However, Griff manages to provoke Marty by calling him "chicken", which eventually results in Marty being chased by Griff and his gang on Hoverboards throughout Courthouse Square. Ultimately, the chase concludes with Griff and his gang crashing through the front windows of Courthouse Mall, which results in them getting arrested instead of Marty Jr.
- After a conversation with an elderly man named Terry, Marty decides to purchase Grays Sports Almanac at the Blast from the Past antique shop, intending to take it back to 1985 and use it to become rich. Shortly after, Marty meets up with Doc, who had retrieved Einstein from the suspended animation kennel, and they discover that their plan has succeeded and that they can go home. However, Doc discovers the almanac and, after chastising Marty, walks up to a mobile trashcan to throw it away.
- Marty and Doc witness the still-unconscious Jennifer being found by police officers Reese and Foley, who believe her to be the Jennifer of the future and take her to her and Marty's future home in Hilldale. After throwing away the almanac, Doc and Marty return to the DeLorean and depart for Hilldale. However, unbeknownst to Marty and Doc, Biff Tannen had overheard them and pursues them in a Taxicab.
- Jennifer is brought to her future home and, not knowing how to use the thumb pad, hides inside the closet from her future relatives from her future family.
- Landing outside of Hilldale, Doc instructs Marty to stay with the car and change clothes and then leaves to retrieve Jennifer, taking Einstein with him. However, after changing his clothes, Marty saw an automatic dog-walker in the distance and, fascinated, wandered off to explore future Hilldale, leaving the DeLorean unattended. Taking of advantage of the opportunity, Biff steals the DeLorean, intending to travel back to 1955 and deliver Grays Sports Almanac to his younger self.
- During family dinner, future Marty receives a call from Douglas J. Needles, who attempts to convince him to join in on an illegal scam, which involved the use of Marty's CusCo credit card, to make more money. Marty is hesitant at first, but goes along with it when Needles calls him "chicken". Unfortunately, their boss, Ito T. Fujitsu, is monitoring the entire transaction and fires Marty on the spot, sending a fax stating "YOU'RE FIRED!!!" which appears in all the fax machines in the house. Jennifer, who had moved from hiding in a closet to the bathroom, takes the fax from the machine there.
- Jennifer runs into her older self, who has just come home. Shocked, both of them faint. Marty and Doc then start carrying the unconscious Jennifer back to the DeLorean.
- Not knowing how to operate the time machine, Biff whacks the display of the Time circuits with his cane, which results in him inadvertendly traveling back to the Cretaceous Period. This creates Timeline 6, which begins at old Biff's entry point in the Cretaceous Period and Timeline 5 fades away.
- Wednesday, October 21
- If old Biff had not erased this timeline, Marty Jr. would eventually have had a son named Marty McFly III, who would have worked at CusCo at some point in the 21st century.
- Back to the Future
- Back to the Future Part II
- Back to the Future: Untold Tales and Alternate Timelines – Issue 3: "Jurassic Biff"
- In Back to the Future: The Card Game, Marty McFly III's FAQ states that he's from a timeline where George had a story published, Lorraine and George became parents, Marty got injured in a car crash, and Griff and his gang went to jail instead of Marty Jr.
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