In 1985, Marty McFly is a typical teenager living in Hill Valley, California. At home, Marty's cowardly father George is bullied by his supervisor, Biff Tannen. His mother Lorraine is an overweight, depressed alcoholic, and his older siblings are professional and social failures. An aspiring musician, Marty's band is rejected for a music contest. He confides in his girlfriend Jennifer Parker about fears of becoming like his parents, despite his ambitions.
That night, Marty meets his eccentric scientist friend Emmett "Doc" Brown in the Twin Pines mall parking lot. Doc unveils a time machine built from a modified DeLorean, powered by plutonium he swindled from Libyan terrorists. Doc inputs a destination time of November 5, 1955 – the day he first conceived his time travel invention. The terrorists arrive unexpectedly, opening fire and shooting Doc. Marty flees in the DeLorean, inadvertently activating time travel when he reaches 88 miles per hour (142 km/h).
Arriving in 1955, Marty discovers he has no plutonium to return. While exploring a burgeoning Hill Valley, Marty encounters his teenage father and discovers Biff has been bullying him since high school. George falls into the path of an oncoming car while spying on the teenage Lorraine, and Marty is knocked unconscious while saving him. He wakes to find himself tended to by Lorraine, who becomes infatuated with him. Marty tracks down a younger Doc and convinces him he is from the future. Doc explains the only source capable of generating the required 1.21 gigawatts of power for time travel is a lightning bolt. Marty shows Doc a flyer from the future that documents an upcoming lightning strike at the town's courthouse. Marty's siblings begin to fade from a photo he is carrying with him. He and Doc realize Marty's actions are altering the future and jeopardizing their chances to exist; Lorraine was supposed to meet George instead of Marty after the car accident. Early attempts to get his parents acquainted fail, and Lorraine's infatuation with Marty deepens.
Lorraine asks Marty to the school dance. He plots to feign inappropriate advances on Lorraine, allowing George to intervene and "rescue" her. The plan goes awry when Biff's gang interrupts and locks Marty in the trunk of the performing band's car, while Biff forces himself onto Lorraine. George arrives expecting to find Marty, and Biff bullies him into submission. After Biff hurts Lorraine, an enraged George knocks him unconscious. He escorts a grateful Lorraine to the dance. The band frees Marty from their car, but the lead guitarist is injured in the process. Marty takes his place and performs while George and Lorraine share their first kiss. With his future no longer in jeopardy, Marty heads to the courthouse to meet Doc.
Doc discovers a note from Marty warning him about his future and destroys it, worried about the consequences. To save Doc, Marty re-calibrates the DeLorean to return ten minutes before he left the future. The lightning strikes, sending Marty back to 1985, but the DeLorean breaks down, forcing Marty to run back to the mall. He arrives as Doc is being shot. While Marty grieves at his side, Doc sits up, revealing he pieced Marty's note back together and wore a bulletproof vest. He takes Marty home and departs to the future in the DeLorean.
Marty wakes the next morning to discover his father is now a successful, confident author, his mother is fit and happy, his siblings are successful, and Biff is a servile valet in George's employ. As Marty reunites with Jennifer, Doc suddenly reappears in the DeLorean, insisting they return with him to the future to save their children from terrible fates.
Michael J. Fox as Marty McFly:
Christopher Lloyd as Emmett "Doc" Brown:
Lea Thompson as Lorraine Baines-McFly:
Crispin Glover as George McFly:
Thomas F. Wilson as Biff Tannen:
James Tolkan portrays Hill Valley high school principal Strickland in both 1955 and 1985. Back to the Future features a 1985-era cast that includes Claudia Wells as Marty's girlfriend Jennifer Parker, and Marc McClure and Wendie Jo Sperber as Marty's siblings Dave McFly and Linda McFly respectively. Elsa Raven portrays the Clocktower Lady. Singer Huey Lewis cameos as a judge for the Battle of the Bands contest. Richard L. Duran and Jeff O'Haco portray the Libyan terrorists.
The 1955-era cast includes George DiCenzo and Frances Lee McCain as, respectively, Lorraine's parents Sam and Stella Baines, and Jason Hervey as Lorraine's younger brother Milton. Biff's gang includes Jeffrey Jay Cohen as Skinhead, Casey Siemaszko as 3-D, and Billy Zane as Match. Norman Alden plays the cafe owner Lou and Donald Fullilove appears as his employee (and future mayor) Goldie Wilson (Donald Fullilove). Harry Waters Jr. portrays Chuck Berry's cousin Marvin Berry, Will Hare appears as Pa Peabody, and Courtney Gains portrays Dixon, the youth who interrupts George's and Lorraine's dance.