The search for Luke
An Imperial Star Destroyer dispatched by the Sith Lord Darth Vader, continuing his quest for Luke Skywalker, dispatches thousands of probe droids across the galaxy, one of which lands on Hoth and begins its survey of the planet. Luke Skywalker, on patrol astride his tauntaun, discovers the probe, which he mistakes for a meteorite. After reporting to comrade Han Solo, he is knocked unconscious by a deadly wampa creature.
When Luke does not come back to Echo Base, Han Solo goes out on his tauntaun to search for him in an encroaching storm. Upon waking up, Luke finds himself hanging upside down in an ice cave; his eyes opening to the sight of another wampa eating his tauntaun. Using the Force, Luke is able to pull his lightsaber towards himself. After he ignites it, he cuts himself free and cuts off the attacking wampa's arm, running out of the cave; and escaping into the cold night of Hoth.
Luke tries to make his way to Echo Base on foot, but he finds himself caught in a blizzard and collapses in the snow. Suddenly, he sees the Force ghost of Obi-Wan Kenobi appear before him. Ben tells Luke to go to Dagobah to undergo training under Yoda, a Jedi Grand Master. After the spirit disappears, Han rides up to an almost unconscious Luke, who is mumbling indistinctly about Ben, Yoda and Dagobah. At this point, the tauntaun that Han was riding on collapses and dies from the extreme cold. To keep Luke warm during the blizzard, Han uses Luke's lightsaber to cut open the dead tauntaun and places Luke in it. Han then sets about erecting a shelter that he and Luke will stay in during the night. They are forced to stay out during the night as the aircraft (snowspeeders) that the Rebels use for atmospheric flight had not yet been adapted for the extremely low temperatures of the Hoth night and are therefore unable to mount a rescue operation to retrieve Han or Luke.
The next morning, Rebel Pilots flying the snowspeeders set out from Echo Base to search for the missing men. Zev Senesca, one of the pilots in Rogue Group makes contact with Han over comlink and the pair are rescued. When they are taken back to base, Luke is put in a bacta tank for healing under the care of medical droid, 2-1B.
Princess Leia Organa tries to urge Han to stay with the rebels, and when Han assumes it is because she has feelings for him, Leia loses her temper and calls him a "stuck-up, half-witted, scruffy-looking nerf herder."
Meanwhile, the probe droid has spotted signs that indicate Hoth is occupied and sends a signal to the Imperial fleet, shortly before being destroyed by Han Solo and Chewbacca. Aboard the Executor, Admiral Kendal Ozzel dismisses the information as evidence of smugglers, nothing more. However, Darth Vader knows better and orders the fleet to Hoth. General Rieekan, realizing the Empire is probably aware of their location, orders the evacuation of Echo Base to begin.
The Battle of Hoth
Darth Vader and the Imperial forces set course for the Hoth system to set up the attack. The rebels load whatever equipment they can onto transports and plan a rear-guard action to secure their escape. Luke, now fully recovered from the Wampa attack and subsequent exposure, says farewell to Chewbacca and Solo, who have decided to leave the Alliance to resolve their debt to Jabba the Hutt. As the Imperial forces enter the Hoth system, General Rieekan orders full power to the energy shield that is protecting the base from orbital bombardment.
Aboard the Executor, Vader senses Admiral Ozzel has emerged from lightspeed so close to Hoth that the Rebels have been alerted to the fleet's arrival. Via video communication, Vader Force chokes Ozzel to death for his incompetence, then appoints Captain Piett the new Admiral on the spot. As Vader previously ordered, the Imperial ground forces, commanded by General Veers, land outside the Rebels' shield and march overland to destroy the power generator.
Princess Leia gives the Rebel fighters instructions on the evacuation to leave Hoth two to three ships at a time past the energy shield to a rendezvous point, which is beyond the outer rim. Rieekan raises the shields to fire the Ion cannon at one of the Imperial Star Destroyers allowing the first transports to escape. The Rebel pilots assigned to hold off the Imperial ground assault depart the Hoth base for the oncoming battle against heavily equipped Imperial forces, who are armed with agile AT-STs (All Terrain Scout Transports) and monstrous AT-AT (All Terrain Armored Transport) walkers, led by General Veers.
The snowspeeder group, led by Luke, commences the attack, but realizing the AT-AT's armor is too strong for blasters, decides to use attached harpoons and tow cables to tangle the walker's legs. Luke's gunner Dak Ralter is hit and killed during the first approach so Wedge Antilles and his gunner Wes Janson take the first shot and manage to destroy one of the AT-ATs. The main AT-AT, commanded by General Veers, prepares to take their aim at the Rebel base's main power generator. Suddenly, Luke's speeder is shot down by the Imperials, and crash-lands in the snow. Luke escapes before the AT-AT can step on and crush his ship.
The Rebel base is now under direct attack and Imperial snowtroopers have entered the base, forcing Han, Leia, Chewbacca, and C-3PO to escape. Leia gives the evacuation command for the base as they leave.
Luke, meanwhile, manages to destroy another AT-AT by using his hoist cable and lightsaber to get into the belly of the transport, tossing in a Thermal Detonator, and then detaching himself from the cable as a series of explosions neutralize the AT-AT. The Rebels suffer major casualties as the result of the battle. The main AT-AT, being driven by General Veers, gets within firing range of the power generator, then successfully blasts and destroys it.
Han, Leia, and company, now realizing they are being followed by Vader (who has arrived personally on Hoth), make their way to the Millennium Falcon in time to escape. As the Falcon flies off, Luke reaches R2-D2 and his X-Wing starfighter and finally departs Hoth. Changing course from the rendezvous point, he sets his coordinates for Dagobah.
Han and company are pursued by Imperial TIE fighters. Flipping the switch to take them to lightspeed, Han realizes (with reluctant help from Threepio) that the hyperdrive has been damaged. While trying to fix the hyperdrive system, Han enters an asteroid field to hamper pursuit. He manages to land inside one of the larger asteroids to rest and find a way to fix the ship.
The destiny of a Jedi
Luke lands on the marshy planet Dagobah, swamping his X-Wing in the process. There, he discovers a diminutive and eccentric figure who fiddles around with Luke's gear. After Luke tells him that he is looking for a Jedi Master, the being offers to take Luke to Yoda.
Back on the Falcon, while Leia tries to make repairs, Han makes his move on the Princess, drawing himself closer to her before both end up in a passionate kiss. When Threepio arrives, Leia withdraws and walks away.
Vader orders the entirety of Death Squadron to begin sweeping the asteroid field to find the Millennium Falcon As the search continued, the dangers of the field begin to take their toll: an asteroid smashed into the bridge tower of a Star Destroyer, presumably killing all aboard. On the Executor, Vader communicates with the captains of the other ships (the captain of the destroyed star destroyer puts his arms up in shock, and the transmission fades). One officer, Captain Lorth Needa, tells Vader that they should consider their damage. Vader firmly replies that they will continue the search. Shortly afterward, Admiral Piett informs Vader that Emperor Palpatine commands he make contact with him. Vader orders his ship out off the asteroid field for a clear transmission.
In his private quarters, Vader receives a holographic message from Palpatine, alias Darth Sidious, who alerts the Dark Lord to a "new enemy who could destroy" the Empire - Luke Skywalker. Vader suggests that if Luke could be turned, he would be a "powerful ally". Lord Sidious agrees, saying that Luke would be a "great asset" and asks his apprentice if it could be done. Vader declares Luke will join the Empire "or die".
Instead of going straight to Yoda, Luke is brought to the creature's hut. Luke insists on going to find Yoda immediately, but the small creature only responds with "Not far Yoda is, not far." The diminutive figure then declares the boy lacks patience, but the voice of Kenobi tells the figure that the boy will learn patience if he is to be trained. Only then does Luke realize that the small green figure is Yoda. Yoda asks Kenobi if he will finish whatever training he begins, then suspects that Luke will be afraid at some point.
The next day, the Falcon manages to escape what turns out to be the mouth of a space slug (who resided in the asteroids the Falcon landed in). Meanwhile, Luke begins a rigorous training regime from Yoda which includes moral lessons about the dangers of the dark side of the Force. That particular lesson is driven home when he is told to enter a cave that is strong with the Dark Side's power. Ignoring Yoda's counsel to leave his weapons, Luke enters the cavern armed. Once inside, he has a vision of himself angrily confronting Darth Vader and beheading him. However, the severed head's mask bursts apart and reveals Luke's face underneath; it is a warning that if Luke battles Vader with no emotional control, he will become Vader himself, seduced by the Dark Side.
Back on the Star Destroyer, Vader enlists the bounty hunters, Boba Fett, Dengar, IG-88, Bossk, 4-LOM and Zuckuss to find the Millennium Falcon for a "substantial reward". One of the Imperial commanders finally spots the Falcon, leading to another pursuit which results in the Falcon eluding the Empire by making the insanely counter intuitive move of attacking the lead Star Destroyer. However, at the last moment, the ship veers off and secretly attaches itself to the ship, which is not extensively covered by sensors, making it appear to have vanished in the Empire's point of view.
Days later, while training, Luke finds that his X-wing fighter has almost completely submerged into the swamp, then breaks concentration. Luke declares he will never be able to get the ship out, seeing that it is too big for him to extract from the water. Yoda says it is "no different, only different in your mind." Luke says he'll "try" to lift the ship, but Yoda says "No! Do or do not, there is no try." Luke tries to use the Force, but to no avail. Yoda reminds him that "size matters not" and gives him wisdom about the Force. Luke denies all of this, then Yoda decides to use the Force to lift the ship out himself. Luke is dumbfounded and incredulous. Yoda senses the youngster's failures within his mind.
When the fleet disperses to search for the Falcon, the Rebels wait for the ship to do its standard dump of refuse before jumping, then detach to float away with it. The Falcon's hyperdrive needs repairs, so Han decides to make their way to Cloud City, a gas-mining colony run by his "old friend" Lando Calrissian. Unfortunately, the bounty hunter Boba Fett had deduced the Falcon's escape method and had his ship jettisoned with the waste to stealthily follow the fugitives.
The next day, Yoda reminds Luke of the things the young Jedi will see in his mind, the future, the past, and of friends he recognizes. Luke breaks concentration again and has a vision of his friends in danger. He wants to leave Dagobah to rescue them. Yoda reminds him that if Luke leaves now, everything his friends fought and suffered for will be destroyed.
The city in the clouds
Upon arrival at Cloud City, Han's party is welcomed by Lando. However, there are numerous elements that make the Rebels suspicious, not the least of which being C-3PO being found deactivated, dismembered, and almost recycled.
That evening, Luke and Artoo prepare themselves to leave Dagobah, but are warned by both Yoda and the spirit form of Kenobi not to end training so soon for a fight Luke is not ready for. Ben declares that should Luke decide to face Vader, he will have to face him alone without interference. Luke understands this, and his ship takes off from Dagobah. Yoda is disappointed, declaring Luke reckless. Ben tells Yoda that Luke is the Jedi's last hope, but Yoda answers back, "there is another..."
A day later, Han and company find themselves betrayed by Calrissian who was approached by the Empire before the Rebels' arrival and threatened him and the city unless he cooperated. They became the captives of Darth Vader, who proceeds to torture Han to create a disturbance in the Force for Luke to detect.
That afternoon, Vader enters a carbon-freezing chamber intending to freeze Luke Skywalker once he arrives. The Dark Lord uses the opportunity for Boba Fett to deliver Solo to Jabba the Hutt (to whom Han owed a debt) by testing the device on Solo himself. Han and company enter the chamber for the experiment. At first, Chewbacca resists the stormtroopers, but Han restrains him, saving his strength for another time. Han says goodbye to Leia with a passionate kiss before he is escalated into the carbon freezing chamber. When he is successfully entombed in carbonite in a state of suspended animation, Vader hands over Han to bounty hunter Boba Fett for transportation to Tatooine to receive a bounty from Jabba. One of the Imperial commanders informs Vader that Luke's starfighter has arrived on Bespin. The Dark Lord orders Lando to take Leia, Chewbacca, and Threepio to his Star Destroyer, reneging on a deal he made with Lando. But the Cloud City administrator has other plans.
Duel with the Dark Lord
Luke makes his way to Bespin safely. He quietly walks down the corridors of Cloud City. He spots Boba Fett who is taking the now-frozen Solo back to his ship. He attempts to follow but is thwarted when the bounty hunter notices and opens fire. Luke narrowly escapes and runs down farther into the corridor. He finally meets up with Leia, Chewie, and Lando, who have been captured by stormtroopers. Luke tries to ambush the group of Imperials, but is unsuccessful. Leia yells at him and tells him that "it's a trap!" Luke runs after his captured friends, hoping to save them, but wanders into the carbon-freezing chamber. There, he meets with Vader and the two fight in an epic lightsaber duel, where Luke's undeveloped Jedi skills are no match for Vader.
The Imperials (escorting the Rebel prisoners out of Bespin) are overpowered by Cloud City security, setting Lando and company free. Chewbacca turns against Lando for betraying Han and chokes him, but he manages to tell the Wookiee there's still a chance to rescue Han at the East Platform. Threepio is reunited with his companion Artoo. Lando and company arrive too late as Fett's ship takes off, then engage in a fierce battle with stormtroopers.
Luke and Vader continue their lightsaber battle in the bowels of Cloud City, just nearly freezing Luke in the carbon freezing chamber. Vader uses the Dark Side of the Force against Luke by using whatever equipment is at hand, eventually thrusting Luke through a window and landing on one of the emergency platforms.
As the gunfight continues, Lando orders an evacuation of Cloud City, then the company manages to find their last hope of escape...the Millennium Falcon.In the final phase of the lightsaber duel, Vader manages to cut off Luke's right hand, which then falls (along with the lightsaber which the hand grasped) into an abyss. In perhaps one of the most memorable scenes in cinema history, Vader reveals to Luke the truth about his father. He did not kill Luke's father, he is Luke's father.
A horrified Luke screams in denial. Vader attempts to persuade Luke to join him and embrace the Dark Side to defeat the Emperor. However, Luke chooses suicide over being corrupted and throws himself down a deep shaft.
Luke is sucked into an air vent, exits the underbelly of the city and catches an antenna beneath Cloud City. Facing clear death, Luke calls out to Ben Kenobi in vain (Kenobi swore not to help Luke once he faced Vader). Then, he calls out to the only other one who could help... Leia.
Leia mysteriously senses Luke's telepathic distress signal. The Falcon turns around and comes back to Cloud City. Using an escape hatch, Lando manages to catch Luke and rescue him before the wounded Jedi falls helplessly to the planet as TIEs race toward them. The Falcon finally leaves Bespin's gravitational field and is about to escape into hyperspace when the hyperdrive system again fails. Vader asks for confirmation that the Millennium Falcon's hyperdrive system was deactivated to prevent their escape, then orders weapons be set to stun.
The Rebels regroup and plan to rescue Han.
As the Imperials pursue the Falcon, the injured Luke telepathically hears the voice of Vader calling to him. He answers, "Father...", while Vader telepathically calls, "Son, come with me". Luke senses it is Vader, then cries, "Ben, why didn't you tell me?"
Threepio commands that Artoo finish reconstructing him after his ordeal in Cloud City. However, with quick ingenuity, Artoo manages to re-activate the Falcon's hyperdrive system just in time for the ship to flee to hyperspace. Vader is disappointed and retreats to his secret quarters in his Star Destroyer, ignoring Piett's failure.
The film ends on a Nebulon-B Class Medical Frigate at the Rebel fleet's rendezvous point, where Luke under the care of 2-1B again which includes the implantation of a prosthetic hand. Lando and Chewbacca begin their parts of a most dangerous mission...rescuing Han. Lando promises to Leia they'll bring her back the man she loves. Luke, Leia, and the droids look on as the Falcon departs for unknown territories.