"The Unknown" is the first episode of the Star Wars: The Clone Wars television series' sixth season, which premiered on the German TV network Super RTL on February 15, 2014. It was released in the US and Canada via Netflix on March 7, 2014.
"Clone trooper Tup succumbs to a mysterious mental illness that results in the shocking death of a Jedi Master. Unable to account for his murderous actions, Tup is sedated and sent back to Kamino for examination. Anakin and ARC trooper Fives accompany Tup, but their return trip is ambushed by Separatists."
On a mission to retake the ring space station in Ringo Vinda's orbit, Jedi Knight Anakin Skywalker and twin Jedi Masters Tiplar and Tiplee lead several clone trooper detachments against the occupying droid force under Admiral Trench, among them are Clone Captain Rex, ARC trooper Fives, and clone trooper Tup. However, Tup has been lately plagued by strange mental disorders which leave him temporarily confused. When the Jedi and clone forces fight their way into the station's command center, Tup suddenly goes into some form of trance, constantly muttering, "Good soldiers follow orders." Upon seeing Tiplar while in one of those blackouts, Tup unexpectedly sneaks up on her and kills her with a blaster shot to her head. This unexpected attack disrupts the battle's schedule and the composure of the Republic troops, forcing them to retreat.
Tup is checked for medical disorders, but strangely no clues to his bizarre condition, which makes him alternate between trances and clear moments where he has no memories of his blackouts, are found. Suspecting a Separatist plot behind this irrationality, Anakin decides to have Tup brought back to Kamino for a more thorough check. Tiplee speculates that the breakdown may have been the result of a rumored anti-clone virus developed by the Separatists. Trench, who had also witnessed the clone's strange disorder, contacts Count Dooku. Dooku initially believes that the clone just simply betrayed the Jedi, but when Trench explains the clone appeared to be under some form of trance, Dooku becomes alarmed. He then contacts his Sith Master, Darth Sidious, concluding that Tup's behavior might prematurely reveal their true plans for the war, and the two Sith decide to abduct the clone before the Republic can examine him.
The Republic prepares a Rho-class transport shuttle to bring Tup to Kamino, with Fives promising to have a drink with him once he returns. As the transport leaves the space station and prepares to make the jump to hyperspace, one of the pilots finds contact up ahead. A HMP droid gunship with five B2 super rocket troopers ambush the convoy. The rocket troopers disable the escorting fighters, while the gunship fires a discord missile and the resulting buzz droids kill both pilots, but one of them manages to send a distress signal before he is killed. The clones guarding Tup soon realize they are under attack and grab their blasters to defend Tup. While one of the medical officers manages to take down two of the super battle droids, all of the clones are eventually killed. The remaining droids then free Tup from the medical table and place him into a container before departing back to Separatist space.
Upon investigating the shuttle's wreck, Skywalker, Rex and Fives swiftly notice Tup is missing and conclude that his strange malady is somehow of great interest to the Separatists. Following the signal from Tup's communicator, they sneak their way to the ring station's main hangar just as Tup is brought aboard a shuttle, but find it too heavily guarded to fight their way to the ship. Just before the shuttle leaves the hangar, however, Fives gets the bright idea to use grappling lines to catch a ride on the shuttle just as it leaves the hangar; the three thereupon board the ship, disable the droid crew and return to their own lines to prepare another transport to Kamino. Fives persuades Rex to allow him to accompany the transport, and the two depart with their stricken comrade for Kamino.
Ringo Vinda, the planet shown at the beginning of the episode, was based on concept artwork for a ringed planet during production of Star Wars: Episode III Revenge of the Sith. In addition, the characters Tiplee and Tiplar's designs were derived from concept artwork for a female Sith that was cut from Star Wars: Episode II Attack of the Clones. The Clone Commander Doom's design was derived from that of the Marvel Comics villain Doctor Doom. The episode featured an updated design of the B2-RP super battle droids, the B2 super rocket trooper, resembling the female Zentraedi power armor in the animated series Robotech.
Although the transport used to carry Tup to Kamino was referred to as a "medical frigate," its design in the episode was a Republic frigate.