Luke Skywalker, riding patrol on a tauntaun, sees the "meteorite" and calls Han Solo, who is also riding patrol. He reports that he hasn't picked up any life readings and that he'll return to the base shortly once he checks out the meteorite.
Just as he is about to start out, Luke is attacked by the Wampa ice creature, a gigantic white-furred monster. The beast drags him away through the snow.
Han, meanwhile, returns to the base and informs the Rebel general, Rieekan, that he has to leave, since Jabba the Hutt put a price on his head. After saying an abrupt farewell to Princess Leia, he starts back toward his ship, but an argument in the corridor ensues.
As Han and Chewbacca try to get the Millenium Falcon ready to go, C-3PO informs him that Leia is trying to get a hold of him, since she's worried about Luke, who hasn't returned yet. Han asks the deck officer, who goes to check if Luke came in through the south entrance, and then goes back to where the Rebels are working on the speeders. The speeders don't work yet, however, so Han goes out to search for Luke on a tauntaun.
Night is falling, however, and the gigantic shield doors of the base must be closed, with both Luke and Han out in the bitter cold.
Luke, meanwhile, having managed to escape from the ice creature, collapses in the snow. As he looks up, he sees the apparition of Obi-Wan Kenobi, his old mentor who was killed by Darth Vader. The ghost instructs him to journey to a planet named Dagobah, where Luke can receive training from a Jedi Master named Yoda. Obi-Wan fades away just as Han approaches.
Just as Han reaches Luke, his tauntaun collapses. Using Luke's lightsaber, he slices open the body. The tauntaun's lingering body warmth will keep Luke warm until Han can get a shelter built.
The next morning, snowspeeders set out to find Han and Luke. A pilot named Zev is the one to find them. They have survived the night intact. Luke's injuries are healed in a bacta tank. As he is recovering, he is visited by the droids, Leia, Han, and Chewie. Han angers Leia, who gives Luke a kiss on the lips. Just then, they are called out because the base is picking up a strange signal.
Threepio can't identify it, saying it could be an Imperial code. Han and Chewie go to check it out. The source of the signal is the Imperial probe droid. After Han hits it with only one shot, the droid self destructs. Knowing that the Empire almost certainly knows where they are, they begin to evacuate.
On the Super Star Destroyer, a ship many times larger than a Star Destroyer, Captain Piett informs Admiral Ozzel that they have a lead on the Rebel base. Ozzel starts to dismiss it, but Darth Vader appears and confirms that the location is correct. The fleet goes into hyperspace toward Hoth. Ozzel, counting on surprising the rebels, brings the fleet out of lightspeed almost on top of of the planet. The rebels erect a strong defense shield, however, so the Imperial will have to conduct a ground assault. Vader uses the force to choke Ozzel to death, promoting Piett to Admiral in his place.
Meanwhile, the Rebels are struggling to get everything ready to leave. Several soldiers and fighter pilots will stay behind to hold the Imperials at bay while the transports are launched. Luke, who has been placed in charge of the remains of Red Group, the same group he flew in at Yavin, says farewell to Han and Chewie before going to meet his ship and his gunner, a young man named Dack. The group, under the new name Rogue Squadron, takes off, preparing to fight whatever the Empire sends against the base.
The transports begin to leave, aided by a small fighter escort and an ion cannon, which takes out anything in the way. The resistance is confronted by six AT-AT's, or All Terrain Armored Transports. The armor is too strong for the blasters of the Rebels, so Luke commands the squadron to use tow cables to trip the huge four-legged machines. Luke's snowspeeder is hit by a stray blast and Dack is killed, however, so Wedge Antilles and his gunner, Wes Janson, take the shot. They attach a cable to one of the AT-AT's legs, then wind it around several times. The machine falls forward and explodes.
Good news like this is rare, however, and the AT-AT's start to break through the Rebels' defense. Luke does manage to blow up another one after his speeder is shot down. He uses a cable to hoist himself to the belly of the transport, then tosses a bomb into a compartment.
Still, the Rebels are forced to retreat. Leia can't get to her own transport, so Han gets her out on the Millenium Falcon. They almost don't make it. Luke makes it back to his X-wing, where he sets out not for the rendezvous point but for Dagobah.
Han and Leia, chased by a Star Destroyer and heading straight for two more, try to go to lightspeed, but something's wrong with the hyperdrive. As Han tries desperately to repair it, they encounter an asteroid field. Insanely, Han heads straight into it. After a stint of dodging through the asteroid field in which most of the TIE fighers chasing them are destroyed, they enter a canyon in one of the large asteroids and lose the rest of their attackers. Then Han sees a cave and guides the Millenium Falcon into it. They are safe for now.
Meanwhile, Luke, accompanied by Artoo, reaches Dagobah. The fog results in almost no visibility, causing him to crash land in the middle of a swamp. His X-wing sinks partially. After making camp, Luke and Artoo meet a diminuative creature who offers to guide Luke to the Jedi Master Yoda.
Inside the asteroid cave, Han, Chewie, Threepio, and Leia struggle to repair the Millenium Falcon's hyper drive. Han and Leia find a brief moment to discover their feelings for each other, but are interrupted by Threepio.
The Imperials are searching the asteroid field for the Rebels. Admiral Piett approaches Vader and informs him that the Emperor wishes to talk with him. Vader talks to Emperor Palpatine's hologram, promising that Luke Skywalker will turn to the dark side of the Force--or die.
Back on Dagobah, the little alien has taken Luke to his hut and is trying to feed him before taking him to Yoda. It isn't until the alien sighs at Luke's impatience, saying that he cannot teach him that Luke realizes that this is in fact Yoda himself. Yoda is reluctant at first to accept Luke as a student, but Ben's spirit helps Luke convince him.
Leia, while sitting alone in the Falcon's cockpit, sees a mynock, a flying creature that inhabits space. Since mynocks can damage ships, Han decides to leave the ship to make sure none are chewing on the power cables. Leia and Chewie go with him. It was mynocks, as he thought, but the cave rocks back and forth, making Han suspicious. He shoots a blaster bolt at the ground, and the cave starts moving even more. They return to the ship, and barely make it out, and not before discovering that it was a giant space slug they were hiding in, not a cave.
On Dagobah, Luke has been training not only in the Force, but also in physical exercises. After a run through the swamp with Yoda riding on his back, Luke rests for a time and Yoda tells him something about the dark side of the Force. Yoda then sends him into a cave, telling him the place is strong in the dark side. Luke encounters Darth Vader, and has a lightsaber duel with him. He manages to decapitate him, but the mask explodes revealing the face of Luke himself!
Meanwhile, as Vader hires several bounty hunters to look for the Millenium Falcon, the Imperials have found the freighter. However, something is still wrong with the hyper drive, so Han is forced to try different tactics. He drives straight for the Star Destroyer, then swoops low over the bridge and engages the landing claw to cling to the hull, in a sensory blind spot. The captain of the ship, Needa, thinking that the Falcon has gone into hyperspace, prepares to take the blame.
Luke's training on Dagobah continues. Yoda tests him again when Luke's X-wing sinks into the swamp. Luke tries to use the force to lift the starfighter out of the swamp, but fails. Yoda then stuns him by doing it effortlessly. Luke can't believe it, and Yoda informs him that is the reason he failed.
Vader kills Captain Needa for his mistake, and the Falcon, tantalizingly close, needs a safe port so her hyper drive can be fixed at last. Han and Leia decide to go the the planet Bespin, since Han's old friend Lando Calrissian is the baron-administrator of Cloud City, a Tibanna gas mining station on Bespin. The Imperials dump their garbage before going to hyperspace to search for the Rebels. Han allows the Falcon to float away, disguised as a hunk of garbage, until the Star Destroyer is gone. Then he heads toward Bespin. Unbeknownst to him, they are being followed by Boba Fett, a notorious bounty hunter that is working not only for Vader, but for Jabba the Hutt as well.
Luke is becoming better at sensing the Force. During an exercise, he sees the future, and in his vision, he sees that Han and Leia are in danger. After much consideration, he decides to postpone his training and go to rescue them. Before he leaves, the spirit of Obi-Wan Kenobi appears and tries to dissuade him, but Luke's mind is made up. As his X-wing blasts off, Yoda tells Ben that there is another hope if Luke fails.
The Millenium Falcon arrives at Bespin and is allowed to land in Cloud City. Lando, after pretending to be angry at Han, greets him as a dear old friend and welcomes the Rebels into his city. Threepio, having dropped a bit behind, investigates a side room after hearing an R2 unit. He discovers stormtroopers, but is blasted to pieces before he can warn the others. Chewie finds him in a junk pile and brings him to Han and Leia, but Lando invites them to dinner, so Threepio is left in pieces in a box. Just as Lando is telling them that he had made a deal to keep the Empire out of Cloud City, he opens a door to reveal Darth Vader himself. He has betrayed Han, though he had no choice in the matter.
Vader wants to freeze Luke in carbonite to ship him to the Emperor, but there are no guarantees as to safety, so he decides to test the facility on Han. Han is frozen in a slab of carbonite, and survives in perfect hibernation. As Han is being taken away by Boba Fett, Luke arrives.
Lando is ordered to take Leia and Chewie to Vader's ship, but the gambler has a trick up his sleeve. His aide, a cyborg named Lobot, brings a team of soldiers that imprison the stormtroopers with them. Chewie starts to strangle Lando once he is freed, but lets him go when they realize that there is still a chance to save Han. They are too late to stop Boba Fett, but are able to escape to the Falcon.
Luke encounters Vader, and they start to duel. Vader is impressed at how far Luke has come in his training, but soon starts hurling heavy objects at him with the Force. Luke falls through a window into the city's central wind tunnel, but manages to pull himself up onto a platform. Vader drives him out onto a narrow walkway over the seemingly bottomless shaft, then slices off his hand with his lightsaber. Luke inches away from him, and Vader chooses that moment to tell Luke, "I am your father."
Luke, who had been told by Obi-Wan that Vader betrayed and murdered his father, is devastated. He allows himself to fall down the shaft, and is sucked into a secondary tunnel, which deposits him on a metal frame hanging from the bottom of Cloud City. Desperately, he calls out to Obi-Wan, but to no avail. Then he tries Leia.
Leia, in the fleeing
At the Rebel rendezvous, Luke is treated by a medical droid, and acquires a real-seeming prosthetic hand. He and Leia see Lando and Chewie off to Tatooine, knowing that Han will end up there sooner or later. Luke, Leia, and the droids will join them later, and try to rescue Han Solo.