The 21 October 2015 has been designated “Back to the Future day”, as it was the day that Marty McFly visited from 1985 in the film Back to the Future II after Dr. Emmett “Doc” Brown persuades Him and his girlfriend, Jennifer Parker, to come back to the future with him to help their future children, who are having trouble with Biff Tannen’s Grandson Griff. Unfortunately Marty unwittingly causes chaos by purchasing Grays Sports Almanac from the future, detailing the results of major sporting events from 1950 to 2000. This is then stolen by the villainous elderly Biff Tannen, while they are distracted by Jennifer, who travels back to 1955 and gives it to his younger self in order to get rich betting on sporting Events, whilst knowing the outcome, Biff then returns to 2015.
Elsewhere Jennifer wakes up in her 2015 home and tries to hides from the McFly family Unfortunately while Attempting to escape the house, Jennifer encounters her 2015 self and they faint. Eventually Marty, Doc, and an unconscious Jennifer return to 1985, unaware of Biff’s actions which have caused an Alternate future where Biff has become fabulously wealthy and corrupt, thanks to the almanac, and has changed Hill Valley into a chaotic dystopian nightmare. Marty’s father, George, was killed in 1973, and Biff has forced Marty’s mother, Lorraine, to marry him. Doc has been committed to an insane asylum.
Doc and Marty discover that in 2015 the elderly Biff used the time machine to change the past. So Marty confronts 1985 Biff, who says he received the almanac on November 12, 1955, then reveals who shot George. Doc and Marty follow Biff to the Enchantment Under the Sea Dance, in 1955 in order to recover the Almanac and undo Biff’s damage to the space-time continuum, Unfortunately though the DeLorean time machine is struck by lightning and disappears. Suddenly, a courier from Western Union arrives and hands Marty a 70-year-old letter from Doc stating that he was sent back to 1885 by the lightning strike. Marty races back into town to find the 1955 Doc who, seconds earlier, has just helped the original Marty from his first time-travel incident go back to 1985.