Brain Invaders " Brain Invaders " is the eighth episode of of the " " television series . It is the thirtieth episode of the series overall . It aired on December 4 , 2009 after a two - week interval and concludes a five - part storyline . Official description . " " When Geonosian brain worm s take control of their supply ship , Ahsoka and Barriss must battle to stop the vessel from unleashing the deadly plague upon the galaxy . " " Plot summary . Padawan s Ahsoka Tano and Barriss Offee are selected to transport medical supplies to Mace Windu on Dantooine from a station near Ord Cestus , while Obi - Wan Kenobi , Anakin Skywalker , Luminara Unduli and Ki - Adi - Mundi prepare to deliver Poggle the Lesser to Coruscant . At the same time , a group of Clone trooper s are resting outside the Progate Temple , where a brain worm hatches from its egg and enters into the nose of one of the troopers , Scythe . Moments later , the company is awakened and informed of their new errand mission to Ord Cestus . They follow the Padawans aboard the medical frigate TB - 73 , with Scythe at the rear carrying more brain worm eggs in his backpack . After the frigate jump into hyperspace , Ahsoka and Barriss lie in their beds , but Ahsoka can ’ t sleep . She thus suggests to Barriss that they should go eat , and they head off to the mess hall . Meanwhile , Scythe enters the troopers ’ sleeping quarters and releases some of the yellow eggs ; the worms hatch and find their way into the noses of the sleeping clones . While the Padawans are eating , Scythe leads two infected clones to kill the ship ’ s pilots , taking control of the bridge . Two other possessed clones , Ox and Edge , enter the mess hall and attack the Padawans , who eventually manage to knock the troopers unconscious . An instant later , two more clones , Trap and Havoc , come through the door . The Jedi question them with lightsabers drawn , but the troopers say they don ’ t know what is going on , and put their guns on the floor . The Padawans then deactivate their lightsabers , and the four of them decide to check if they are still in control of the bridge . After Barriss fails to contact the bridge via comlink , the two Padawans and Trap set off to go there , while Havoc stays to watch the unconscious clones . In a different place in hyperspace , Jedi Master s Luminara and Ki - Adi inform Anakin and Obi - Wan that the medical frigate did not check in on time . Anakin starts to worry for Ahsoka , but Ki - Adi suggests they should focus on interrogating the so far uncooperative Poggle . Concurrently , the infected clones aboard the medical frigate engage the autopilot and security shields , blocking the way for Ahsoka , Barriss and Trap . Barriss tries to override the shield controls , but Trap then fires his blaster at her . She manages to deflect it and disarm him , noticing that he too is infected by a brain worm . He throws himself at her , and she ultimately has to kill him in self - defense . Ahsoka manages to kill the brain worm which has emerged to take possession of Barriss . The Padawans decide to contact Master Fisto and quarantine the ship , but on their way they come across the cargo hold , where the infected troopers are releasing a brain worm into another trooper . They are spotted and realize they are outnumbered , so they escape through the ventilation system . From there , Barriss goes to disable the thrusters , and Ahsoka heads to the communication room to send a warning to Kit Fisto . Ahsoka tells Fisto about the worms , but he insists that the frigate dock anyway in order for a sanitation team to take out the worms . Ahsoka also contacts Anakin , updating him on the situation . On her way to the reactor , Barriss gets temporarily incapacitated by an electric trap and is exposed to a newly hatched brain worm by the troopers . After finishing her transmission , Ahsoka is surprised to see Barriss standing beside her . The possessed Barriss attacks her , and after a brief fight , Ahsoka manages to escape into the ventilation system . In the meantime , Anakin angrily goes to interrogate Poggle , using the Force to try to make him talk , but this doesn ’ t work ; he thus hits Poggle and proceeds to Force choke him . After getting the information he needs , Anakin informs the other Jedi about the brain worms , contacts Ahsoka on her comlink and tells her that the worms are affected by cold temperature , and that she should rupture the coolant system . She does this , releasing freezing air into the ship , just as it comes out of hyperspace . While the clones get weakened by the cold , Barriss finds Ahsoka ’ s trail again and confronts her inside the bridge . They fight , but Barriss and her worm are eventually taken out by the cold . Regaining her own will for a moment , Barriss begs Ahsoka to kill her , but Ahsoka can ’ t bring herself to do so . Barriss attacks again , but Ahsoka manages to kill the worm as it protrudes from Barriss ’ s mouth . The frigate docks at the station , and Kit Fisto boards it with two clone troopers . They find the two frozen Padawans lying on the ground , still breathing , and bring them to the infirmary . When Ahsoka wakes up , Anakin is waiting at the end of her bed , and assures her that everything is all right , and that Barriss and the troopers were saved . Fisto explains the parasite ' s origins , and he and Anakin theorize this was likely how the Geonosian recaptured their planet : Anakin remarks the troops of Geonosis will have to be warned , so such an incident doesn ' t recur . Once Fisto has left , Ahsoka tells Anakin about Barriss begging for death under the worm ' s influence , and wonders if she should have killed Barriss , since had they failed , her refusal could have resulted in the entire medical station being infected . Anakin consoles her with the knowledge Barriss only thought her death was necessary to stop the worms , and that she did the right thing in sparing her friend , since it is a Jedi ' s responsibility to save as many people as they can . Behind the scenes . The Jedi Temple Archives feature on Blu - ray includes the compilation of deleted brain - invading worm scenes " Wormontage " .