Source plot synopsis — includes the ending
On November 12, 1955, moments after witnessing Emmett "Doc" Brown disappear in his DeLorean, Marty McFly learns that Doc was sent 70 years into the past to 1885. Using information from Doc's 1885 letter, Marty and the 1955 Doc find and repair the DeLorean, hidden away by Doc in 1885, so that Marty can return to 1985. After finding it, Marty comes across a tombstone inscribed with Doc's name, erected by the town's then-new schoolteacher Clara Clayton, stating that Doc was killed by Biff Tannen's great-grandfather, Buford "Mad Dog" Tannen, over 80 dollars, six days after writing the letter.
Despite the letter's warning, Marty travels to September 2, 1885, to save Doc, arriving in the middle of a cavalry pursuit of Native Americans. Marty evades the pursuit, but damages the car's fuel line. Chased by a bear, he is knocked unconscious and found by his Irish-born great-great-grandparents Seamus and Maggie McFly, who allow him to stay the night. The next morning, under the alias Clint Eastwood, Marty arrives in a newly founded Hill Valley but runs afoul of Buford and his gang. Doc rescues Marty from Buford's attempted lynching. Doc agrees to leave 1885 after learning his fate, but without gasoline, the DeLorean cannot reach 88 miles per hour (142 kilometers per hour) to time-travel. He proposes using a steam locomotive to push the DeLorean to that speed.
While inspecting a rail spur, Doc saves Clara from falling into the ravine, averting her death from the original timeline. They fall in love. At a town festival, Buford tries shooting Doc, but after Marty intervenes, Buford challenges him to a showdown in two days by calling him "yellow". Doc Brown urges Marty not to react to provocation, letting it slip that Marty's impulsiveness causes a life-changing accident in the future.
Although reluctant to return to 1985, Doc visits Clara to end their relationship and bid her goodbye. She dismisses his story about being from the future. Doc attempts a drinking binge, but passes out after one drink. Buford arrives for Marty, who sees his alias appear in the tombstone photograph and refuses to duel. A revived Doc is captured by Buford's gang, forcing Marty to duel. Marty uses a stove door as a bulletproof vest to survive Buford's shot and, in the ensuing fistfight, knocks Buford into a wagon of manure. Buford and his gang are then arrested for an earlier robbery.
On the train to San Francisco, Clara learns of Doc's heartbreak and runs back to town. She finds the model time machine at his shop and realizes Doc was telling the truth. Doc and Marty use the locomotive to push the DeLorean along the spur line. Clara boards the locomotive and loses her footing. Marty, in the DeLorean, passes his hoverboard to Doc, who uses it to save Clara. The DeLorean hits 88 mph and vanishes as the locomotive plunges from the unfinished bridge.
Arriving back in 1985 on October 27, Marty escapes the disabled DeLorean as a freight train destroys it. Reuniting with his girlfriend Jennifer Parker, Marty declines a street race with Needles, not knowing that he had avoided the accident Doc warned him about. Jennifer opens the fax message she kept from 2015 and watches the text regarding Marty's firing disappear.
As Marty and Jennifer examine the DeLorean wreckage, a steam locomotive time machine appears, operated by Doc, Clara, and their children. Doc gives Marty a photo of them standing next to the town clock in 1885. When Jennifer asks Doc about the blank fax, he says it means their future has not yet been written and encourages them to "make it a good one". Doc and his family bid farewell and fly off in the locomotive.
Despite the letter's warning, Marty travels to September 2, 1885, to save Doc, arriving in the middle of a cavalry pursuit of Native Americans. Marty evades the pursuit, but damages the car's fuel line. Chased by a bear, he is knocked unconscious and found by his Irish-born great-great-grandparents Seamus and Maggie McFly, who allow him to stay the night. The next morning, under the alias Clint Eastwood, Marty arrives in a newly founded Hill Valley but runs afoul of Buford and his gang. Doc rescues Marty from Buford's attempted lynching. Doc agrees to leave 1885 after learning his fate, but without gasoline, the DeLorean cannot reach 88 miles per hour (142 kilometers per hour) to time-travel. He proposes using a steam locomotive to push the DeLorean to that speed.
While inspecting a rail spur, Doc saves Clara from falling into the ravine, averting her death from the original timeline. They fall in love. At a town festival, Buford tries shooting Doc, but after Marty intervenes, Buford challenges him to a showdown in two days by calling him "yellow". Doc Brown urges Marty not to react to provocation, letting it slip that Marty's impulsiveness causes a life-changing accident in the future.
Although reluctant to return to 1985, Doc visits Clara to end their relationship and bid her goodbye. She dismisses his story about being from the future. Doc attempts a drinking binge, but passes out after one drink. Buford arrives for Marty, who sees his alias appear in the tombstone photograph and refuses to duel. A revived Doc is captured by Buford's gang, forcing Marty to duel. Marty uses a stove door as a bulletproof vest to survive Buford's shot and, in the ensuing fistfight, knocks Buford into a wagon of manure. Buford and his gang are then arrested for an earlier robbery.
On the train to San Francisco, Clara learns of Doc's heartbreak and runs back to town. She finds the model time machine at his shop and realizes Doc was telling the truth. Doc and Marty use the locomotive to push the DeLorean along the spur line. Clara boards the locomotive and loses her footing. Marty, in the DeLorean, passes his hoverboard to Doc, who uses it to save Clara. The DeLorean hits 88 mph and vanishes as the locomotive plunges from the unfinished bridge.
Arriving back in 1985 on October 27, Marty escapes the disabled DeLorean as a freight train destroys it. Reuniting with his girlfriend Jennifer Parker, Marty declines a street race with Needles, not knowing that he had avoided the accident Doc warned him about. Jennifer opens the fax message she kept from 2015 and watches the text regarding Marty's firing disappear.
As Marty and Jennifer examine the DeLorean wreckage, a steam locomotive time machine appears, operated by Doc, Clara, and their children. Doc gives Marty a photo of them standing next to the town clock in 1885. When Jennifer asks Doc about the blank fax, he says it means their future has not yet been written and encourages them to "make it a good one". Doc and his family bid farewell and fly off in the locomotive.
Sources and content license
Source and revision history ↗ · Adapted from Wikipedia contributors, Back to the Future Part III. Section headings and formatting adjusted. · Content license