Marty McFly. All-American boy. He has small-town dreams of being a rock star, gets in just enough trouble at school (okay, maybe a little too much), spends as much time as he can with his girlfriend, Jennifer, and spends whatever time is left with his family.
But he also pals around with the town nutso, Dr. Emmett Brown. Who knows how or why this odd couple found one another… but they did. And now Doc has roped Marty into helping him test out his greatest invention—a working time machine made out of a DeLorean. And oh yeah—it runs on plutonium. That he stole from a bunch of Libyan nationalists. Thank goodness nothing could possibly go wrong.
Except that the Libyans show up. They shoot Doc (apparently to death) and then go after Marty, who escapes in the DeLorean… to 1955. Suddenly, his town is different, the people are different… heck, in this place you can't even get a Pepsi Free. ("You want a Pepsi, pal, you're gonna pay for it.")
As it turns out, Marty's got a few problems.
Number one: 7-Elevens are not yet carrying weapons-grade plutonium, so getting back to 1985 may be an issue.
Number two: there's this bully named Biff (his father's tormentor in 1955 and supervisor in 1985) who keeps getting all up in his business.
And number three: he accidentally interfered with his mother and father's would-be romance, and now has to make sure they still get together so he doesn't become erased… from existence.
Doc and Marty come up with the inspired (and awfully lucky) idea to use the energy from a bolt of lightning that they know is coming (it's good to be from the future) to power the DeLorean back to Marty's present. In the week leading up to the event, Marty does his best to convince his father, George, to take his mother, Lorraine, to the Enchantment Under the Sea dance… but ends up taking her himself. Hopefully he has Oedipus on speed dial.
The idea is to have Marty tick Lorraine off, then have George step in and be the hero. Oh, the best laid plans…
Biff and his crew throw a wrench into things by having Marty thrown into the trunk of a car. Which means that George has to actually beat the stuffing out of a guy twice his size in order to win Lorraine's heart. Note: do not make George McFly angry. You wouldn't like him when he's angry. So yeah, George clocks Biff, and then gets lucky that Lorraine is incredibly attracted to shows of violence. They're totally back on.
Okay, time to return to 1985. After a few little snafus (well, it can't go perfectly, obviously), the lightning trick works and Marty is home at last. Plus, he was able to warn Doc about the hail of gunfire from the Libyans, and Doc prepared himself by donning a bulletproof vest. Good thing none of those bullets hit him in the face.
Things are different now... but in a good way. George is a together, successful guy instead of the sniveling brown-noser he was in the old 1985. Lorraine is no longer an alcoholic, Biff is now completely under George's thumb, and even Marty's house is way less depressing.
Unfortunately, Doc shows up at the last minute and tells Marty and Jennifer there's something wrong with their kids in the future. Fortunately, the obvious sequel is going to provide plenty of additional marketing opportunities.