Lights, camera, action!
An Imperial Star Destroyer attacks a Rebel convoy in search of the stolen plans to their new battle station, the (dun dun dun) Death Star. Leading the campaign is the evil masked man Darth Vader. He and his forces search the entire ship but find no plans, just Princess Leia and a bunch of rebels we will never see or hear from again.
Seriously, what happened to those guys?
Unbeknownst to the Empire, two droids, C-3PO and R2-D2, escaped with the plans and have landed on the desert planet below. They are purchased by a farmer named Owen Lars and his nephew, Luke Skywalker. R2-D2 escapes from Luke's custody to search for someone named Obi-Wan Kenobi. Luke follows the little droid, and after a tussle with some Sand People, they find the one and only Obi-Wan Kenobi. Obi-Wan lays down some truth on the young Luke, telling him about his lightsabers, the Force, and Luke's father's fate.
Imperial stormtroopers, having picked up the droids' trail, locate and murder Luke's family. With no ties to the planet, Luke agrees to go with Obi-Wan to Alderaan and learn the ways of the Force. At Mos Eisley, they charter a ride with Han Solo and Chewbacca, crew of the Millennium Falcon.
Flying the not-so-friendly skies, the Millennium Falcon evades the Imperials and makes the jump to lightspeed. When they come out of hyperspace, they learn that the Death Star has destroyed the planet and—despite their earlier escape—they're captured by the Death Star.
Womp.
Using video game logic, they trick stormtroopers into the Falcon, steal their clothes, and seize a nearby control room. Obi-Wan goes to turn off the power to the tractor beam while Luke convinces Han Solo to help him rescue Princess Leia.
The heroes manage to rescue Leia, and after a quick detour through the trash compactor, return to the Falcon. Obi-Wan turns off the tractor beam but is confronted by Darth Vader on his way back to the ship. With a knowing smile, Obi-Wan willingly perishes at the business end of Darth Vader's lightsaber. Luke witnesses his mentor's demise but escapes with the others… thanks to some otherworldly prompting by Obi-Wan.
Leia leads the Millennium Falcon to the Rebel base on Yavin IV (although she suspects the Empire is tracking them). They totally are. Using R2's data, the Rebels strategize to destroy the Death Star by having a one-man starfighter launch a photon torpedo into a tiny exhaust port connected to the station's reactor. Han Solo decides to skip the suicide run and settle his debt with Jabba the Hut.
The Death Star prepares to destroy the Rebel base while Luke joins the Rebels in their offensive. Most of the Rebels are killed in the fight, but Han Solo returns at the most dramatic moment to save Luke's life. Luke makes the fateful shot, blows up the Death Star, and returns to the Rebels a hero.
One award ceremony later and its happy endings all around—well, except for Darth Vader, who will be lost in space until the sequel.