In a flashback scene, Jedi Knight Obi-Wan Kenobi meets with his Padawan Anakin Skywalker for a lightsaber sparring session. Kenobi asks Skywalker if he is ready before the two parry. In the present, an Imperial captain ushers the Third Sister Reva aboard the bridge of his Imperial Star Destroyer Devastator. Dispensing with the pleasantries, Vader demands to know where Kenobi is. Reva reports that they have tracked Kenobi down to Jabiim. Vader expresses satisfaction before ordering her to kneel in the presence of the bridge crew. After promoting Reva to the rank of Grand Inquisitor, he orders the captain to set a course for Jabiim immediately.
Meanwhile, Kawlan Roken's descends in Jabiim's atmosphere and lands at the Path's base. Roken disembarks with Kenobi, Princess Leia Organa, Tala Durith, and Sully Stark. Kenobi is surprised to see Haja Estree, who reveals that he fled Daiyu after getting into a fight with the Third Sister. In response, the Galactic Empire had placed a bounty on him, making him a fugitive like the Jedi. Haja hopes to exploit business opportunities on Jabiim.
Kenobi speaks with Roken, telling him that he needs to get Leia back to Alderaan on the transport. Roken explains that the other people in the Path base have been waiting for months. Roken explains that they had been planning to use an old trade route but had delayed the trip in order to rescue Leia. Kenobi promises to do what he can to help while Roken tells the fugitives to get ready to depart.
While Vader's Star Destroyer travels through hyperspace, he issues orders to lock down the Path's base. Reva warns that if they trap them, their opponents can hold out for several days. Vader replies that he does not intend to break their enemies. Meanwhile, the reprogrammed L0-LA59 ("Lola") flies into the base's power plant and hacks into its electrical systems, sealing the hangar roof. Kenobi notices a writing on the wall stating that "light will fade but is never forgotten."
As the hangar roof doors seal, Kenobi discusses the situation with Tala, who believes that Reva has tracked them down to Jabiim. Kenobi believes that Vader is leading the hunt and plans to attack the Path's base rather than lay siege to them. When Roken asks how he knows Vader's next move, Kenobi experiences a flashback of dueling with Skywalker in a training session. Skywalker advances aggressively on his master, prompting Kenobi to warn him that the Jedi goal is to defend life rather than to kill.
Skywalker ignores Kenobi's warning and advances on him, countering that mercy does not defeat an enemy. As the two cross blades, Skywalker states this is why he is going to lose. In the present, Vader's Star Destroyer dispatches two starships to attack the Path's base. Kenobi addresses the frightened civilians, telling them that he understands their fear and anxiety. Since they are unable to fight the Empire, he states that they will aim to hold off the Empire long enough until they can reopen the hangar roof. Kenobi tasks Roken and his fighters with reopening the facility's hangar roof within an hour and sealing the other entrances.
As Imperial ships descend, the Path defenders get to work in sealing the remaining entrances. The Imperial ships dispatch a landing part of stormtroopers and elite Purge Troopers, who surround the facility. Several stormtroopers assemble heavy guns. The Imperial troops are joined by Reva, who arrives in a Scythe transport shuttle. She orders them to bombard the outer doors. Tala urges Roken to work on reopening the hangar roof but they encounter difficulties. Haja suggests that Roken and his men enter the vents to investigate what is obstructing the hangar roof but Roken replies that he is too big. Leia volunteers with Kenobi advising her to be careful. He also tells Haja to keep an eye on her while she climbs the ladder.
Kenobi leaves to listen to a message left by Senator Bail Organa on his portable holoprojector. In private, Kenobi sees that Organa is worried by the lack of communication. Organa fears that Vader has found Kenobi or learned about the children, and if he does not hear from Kenobi soon, he will travel to Tatooine to protect Owen Lars and Luke Skywalker. Following the transmission, Kenobi reassures Tala that he will be alright. Tala confides that she took part in an operation to round up four Force-sensitive families on Garel under the cover of arresting people for tax evasion. Tala was traumatized by the death of 14 people including six children at the hands of the Inquisitors. Tala resolves to make amends for her wrongdoings by helping to fight off the Imperial besiegers.
With the outer doors buckling under pressure, Kenobi tells the defenders that he will buy them time by parleying with the Third Sister. During a ceasefire, Reva warns the fugitive Jedi that his stalling attempt will not stop Vader's advance. Kenobi questions how she knows about Vader's identity as Anakin since he believes she was too young to have known him. Kenobi deduces that Reva was a youngling who witnessed Skywalker leading the attack on the Jedi Temple on the night of Order 66. Reva is haunted by her memories of Skywalker killing her fellow youngling friends. She says that she believed that Vader was there to help them and was shocked when he murdered her Jedi "family." Reva reveals that she survived by playing dead.
Kenobi realizes that Reva is planning to kill Vader and asks her to work with him. Reva is distrustful of Kenobi and questions his desire to kill Vader, pointing out that Kenobi was not there to protect her and the other Jedi at the Temple. Reva points out that Skywalker was Kenobi's Padawan and asks why he did not stop him when he had the chance. Reva rejects Kenobi's offer of help and believes that she will triumph over her enemies alone. The Third Sister uses her lightsaber to cut her way through the metal gate.
The Third Sister orders the Imperial attack on Jabiim to begin.
However, Kenobi uses the Force to hurl her back. A gun battle breaks out between Reva's stormtroopers and the Path fighters. Reva orders her troops to storm the breach in the Path's facility. Path fighters including Tala and the loader droid NED-B shoot at the advancing Imperials. Kenobi also joins the fight with lightsaber and strikes down a Purge trooper. Through sheer weight of numbers, the Imperials advance into the Path's facility.
Meanwhile, Haja tells Leia that she is looking for a red breaker. Tala and the Path fighters retreat deeper into the base while Kenobi helps a wounded woman to safety. NED-B also fights several stormtroopers. He manages to hurl two aside. Tala is also hit and falls to the ground. Kenobi attempts to assist her and strikes down several stormtroopers with his lightsaber. NED-B carries the wounded Tala to safety before using his body as a shield against the stormtroopers' blaster bolts. Tala tells Kenobi to retreat before activating a detonator. Kenobi is distraught but seals the inner blast door. Tala blows herself up, delaying the Imperial advance.
Kenobi and the surviving fighters retreat to the inner sanctum of the base only to find that Leia is still trying to open the hangar roof. The Imperial captain informs Lord Vader that Reva has breached the inner sanctum. Vader tells the Captain to order Reva to stand down, believing that Kenobi is in their grasp. In a flashback scene, Skywalker drives to Kenobi to the edge of the balcony and tells his master to admit that he is beaten.
Believing they have lost, Kenobi wants to go back and surrender to Lord Vader. Roken objects, telling Kenobi that Tala's sacrifice would have been in vain. Kenobi is determined to stop Lord Vader's advance in order to save the fugitives inside. Kenobi asks Haja to look after Leia. Roken asks Kenobi how he is going to fight Vader without a weapon, prompting Kenobi to reply that there are other ways to fight. Kenobi walks out of the second blast door and surrenders to the Imperials. He is arrested by two stormtroopers. Other stormtroopers evacuate their wounded and fallen comrades.
While Leia searches through the cables and wires for the red breaker, Lola watches her menacingly. Kenobi is brought to a triumphant Reva, who orders her troops to inform Lord Vader of their capture. Reva informs Kenobi that Lord Vader is on his way. Kenobi counters that he is bringing him to her rather than other way round. He asks Reva if she is going to let Lord Vader slaughter more civilians including children and reiterates his offer to stop Vader again. When Reva asks if he won't see it coming, Kenobi replies that Vader will be too fixated on him.
Two stormtroopers escort Kenobi inside the base. Back in the flashback, Kenobi manages to break out of the corner that Skywalker has maneuvered him into. The two resume their fight but Skywalker still manages to knock the lightsaber out of Kenobi's hand. Kenobi warns his Padawan that his need for victory blinds him. Back in the present, Vader arrives outside the Path fortress and meets with Reva, demanding to know where Kenobi is. She tells her master that Kenobi is inside but Vader is determined to bring Kenobi in himself.
Meanwhile, Kenobi breaks free of his stormtrooper captors and flees deeper into the Path's facility. While searching for the red breaker, Leia is attacked by the reprogrammed Lola. Leia sees that a restraining bolt has been attached to Lola and frees her droid, freeing her of the Imperial programming. Vader enters the base in pursuit of Kenobi while Leia and Lola work together to open the roof doors. Sully leads the refugees aboard their ship while Kenobi reunites with Leia. Leia learns that Tala did not survive.
While Leia and Kenobi head for their transport, Vader forces his way inside the hangar bay. He uses the Force to grab Roken's freighter, preventing the ship from ascending and forcing it to the ground. He rips the ship apart only to find that it is an empty decoy. The Path fighters and refugees escape on a second freighter while Vader watches in fury. Back in the past, Kenobi breaks free of Skywalker in the sparring match and uses the Force to grab his Padawan's lightsaber. Kenobi tells Skywalker that he is a great warrior but that his need to prove himself is his undoing. Kenobi counsels Skywalker to overcome this desire in order to progress from being a Padawan.
Back in the present Reva attempts to stab Vader with her lightsaber but he uses the Force to block her blade. Vader surmises that Kenobi was wise to use the Third Sister against him. He hurls Reva aside. Reva charges but Vader uses the Force to casually deflect her lightsaber and hurls her to the ground multiple times. Reva activates her lightsaber's twin blade spinning mode but Vader uses the Force to stall the blades rotation, and then rips her saber from her grip. Vader detaches her lightsaber into two single hilts, and tosses one on the ground at Reva's feet. Reva retrieves the weapon and continues to attack Vader, but the Sith Lord quickly disarms her again.
Reva is haunted by memories of Vader killing her fellow younglings. Lord Vader stabs Reva through the torso and she falls to her knees. The Grand Inquisitor then appears with several stormtroopers, revealing that he survived, wryly stating that revenge is a wonderful fuel for the will to live. Vader then chides Reva that he deduced her intent to betray him some time ago, but didn't act on it because her rage was a valuable tool in the hunt for Kenobi - now, however, the Third Sister is no longer of use to him. The pair then abandon Reva to die of her wounds, just as she left the Grand Inquisitor.
Aboard Roken's ship, Kenobi and Leia sit among the refugees. Roken tells them the ship's hyperdrive is not working and that the Empire is still pursuing them. Back on Jabiim, Reva reaches for her double-bladed spinning lightsaber and eyes Kenobi's holoprojector. Watching the holoprojector's hologram, Reva intercepts Organa's message and learns that Anakin Skywalker has a son on Tatooine. Kenobi realizes his holoprojector is missing but tells Roken that nothing is wrong. On Tatooine, the young Luke Skywalker sleeps in his bed at the Lars Homestead.