Back To the Future

Plot

It has been six months since Marty McFly witnessed Dr. Emmett Brown disappear into an unknown time. The bank has begun foreclosing on Doc's home. On May 14, 1986, while helping his father George clear out Doc's possessions, Marty is shocked to see a DeLorean time machine (later revealed to be a temporal duplicate created by the lightning strike in the second film) appear outside the house, having previously witnessed its destruction. Inside is Einstein, Doc's dog, and a tape recorder with a message from Doc explaining how the DeLorean would return to this present should Doc fall on hard times. Einstein helps track down Edna Strickland, the elderly sister of Marty's school principal and a former reporter for Hill Valley's paper. Reading her newspaper collection, Marty learns that Doc was arrested in 1931 and killed by Irving "Kid" Tannen, Biff Tannen's father. Marty and Einstein travel to 1931 to prevent Doc's murder.

Marty arrives on June 13, 1931, and learns that Doc was accused of arson upon Kid's illegal speakeasy and thus needs to break out of jail. Doc tells Marty to seek the aid of his younger self, Emmett, who at this point in time assists his father, who staunchly resents Emmett's dream of a career in science, at the courthouse. Along the way, Marty encounters his grandfather Arthur "Artie" McFly, Officer Danny Parker (his girlfriend Jennifer's grandfather), and a young Edna. While convincing Emmett to help, Marty delivers a subpoena to Artie, who serves as Kid's accountant, persuading him to testify against Kid and help prove Doc's innocence. Believing all has been fixed, Doc and Marty prepare to return to the present when Marty starts to fade away. Doc discovers Artie would be killed the next day for testifying, thus erasing Marty's existence. Travelling back in time, they convince Artie to lay low after testifying while avoiding their past selves.

Returning to May 15, 1986, they realize that their actions in the past have prevented the arrest of Kid Tannen, allowing him to expand his criminal operations. As a result of this, the Tannen family became the fifth-most-dangerous crime family in California, owning all of Hill Valley. Marty and Doc travel to August 25, 1931, the day Kid was supposed to be arrested. The duo find another option: they convince Trixie Trotter, Kid's moll who has a soft-spot for Artie, to testify instead. The cop (Danny Parker) who was meant to arrest Kid has been demoted because of Marty and Doc's tampering, causing his girlfriend Betty (Jennifer's grandmother) to dump him and he now works for Kid to earn some extra money. After Marty restores his confidence, Parker decides to turn against Kid to win back Betty. Kid and his gang are jailed, and all appears to be in-order. Doc reveals that this is also the night that motivated him to finish his rocket car experiment for the Hill Valley Science Expo. He went to see Frankenstein when he was stressed and was inspired, even keeping the ticket stub until 1986. Marty and Doc return to the future unaware that their actions have caused Edna to fall in love with Emmett, and their relationship causes Emmett to give up on his scientific inventions. The ticket stub starts to fade out of existence as Doc realizes that Edna stopped him from seeing the film.

When they return to 1986 again, Doc and Einstein disappears, and Marty crashes the DeLorean into a billboard. Dazed, Marty finds Hill Valley has become a totalitarian walled society, run by "Citizen Brown". Sneaking inside, Marty learns that Edna has brainwashed Emmett and used his intelligence to craft a perfect society in her eyes. Marty is able to get close to Citizen Brown and show him a notebook he recovered from 1986 with the first drawing of Doc's flux capacitor. Citizen Brown is flooded with memories and decides to turn against Edna to fix history. He helps Marty repair the DeLorean and the two set off for 1931 to try to undo their previous mistakes. However, the damage causes the DeLorean to arrive in October instead of August, when the Science Expo is about to begin and Edna and Emmett's relationship has strengthened. Marty is ready to take whatever steps are needed to end it, but Citizen Brown becomes worried about what will happen to Edna and angry that Marty does not care about her feelings, and drives off alone in the DeLorean to assess the situation.

Marty, with help from Trixie, ends Edna and Emmett's relationship, but Emmett still is reluctant to return to his scientific roots. Marty tries to force Emmett to see Frankenstein to help him, leading to an argument about Emmett's inability to stand up for himself. A lightning storm erupts causing Emmett to realize that rockets cannot make the car fly. This memory acts as a replacement for Emmett seeing the creature electrocuted in the film as in the original timeline. The answer is static electricity and Marty helps Emmett convert his rocket car to a new propulsion system in time for the Science Expo. Meanwhile, Edna is picked up by Citizen Brown, and when she explains what Marty has done Brown decides to help her thwart Marty's plan. At the Expo, Edna and Brown attempt to sabotage Emmett's project, but Marty discovers them in time. During this, he happens to learn that Edna was responsible for the arson of Kid's speakeasy. During the Expo, Emmett successfully demonstrates his flying car, just as Judge Brown arrives. Marty is able to help Emmett to stand up for his choices. Judge Brown and his son settle their differences, with Emmett's father now accepting his son's scientific views.

Edna is incensed as her plan has been foiled, and when Citizen Brown refuses to help her further she steals the DeLorean, running him over before inadvertently travelling through time. As he dies and disappears (due to Marty fixing Emmett's timeline), Citizen Brown tells Marty he was right about Edna. Marty gives Emmett a sealed note with instructions to be opened in the future. Shortly after, a second DeLorean appears with Doc at the wheel, having been summoned from 1986 by the note. As they talk about events, the town of Hill Valley disappears around them. They find, from Marty's great-grandfather William "Willie" McFly, that the town burned down shortly after its founding in 1876 with Mary "Scary Mary" Pickford (in fact Edna Strickland) its only remaining inhabitant. Travelling to July 17, 1876, Marty and Doc discover a crazed Edna has travelled there and attempted to burn down the saloon run by Beauregard Tannen, inadvertently taking the rest of Hill Valley with it. They stop Edna before she can commit the act while simultaneously saving her from Tannen's shotgun, returning her and the first DeLorean to the restored Hill Valley of 1931. Edna is quickly arrested, having previously been recorded confessing to arson against Kid's speakeasy. The alternate DeLorean then disappears, having been erased from history. As Marty and Doc are preparing to return, Marty spots Artie and Trixie, having fallen in love with each other, and worries about his future since Artie was to be wed to his grandmother Sylvia. She reveals that “Trixie Trotter” is a stage name and that her name is actually Sylvia Miskin.

Doc and Marty arrive in 1986 and discover that in this new post-time-travel timeline, there was no estate sale because Doc's reconciliation with his father allowed the Browns to stay part-time in Hill Valley. They find that Edna and Kid had fallen in love while in jail, and afterwards married and both became much happier and friendlier since. Doc reveals his previous absence to Marty; he had been compiling a history of the McFly family to present to Marty as a graduation gift but found information on his grandmother challenging to come across (as she was working under the name Trixie) and thus had travelled to 1931 to attempt to obtain research first-hand. Suddenly, three separate DeLoreans appear, each with a different future version of Marty driving them. They approach Marty and Doc and insist they come to help assure that their respective futures occur as they are supposed to. Doc and his Marty leave the Marties arguing with each other, saying the future can wait until after they have enjoyed the present for a while; they then depart to an unknown time.