The Hidden Enemy

"The Hidden Enemy" is the sixteenth episode of Season One of the television series Star Wars: The Clone Wars.

Moral
Truth enlightens the mind, but won't always bring happiness to your heart.

Plot
Anakin, Obi-Wan and their clones prepare to ambush the advancing droid forces from two towers. Just as they are about to fire on the droids, the advances split into three columns and droids suddenly appear in Obi-Wan's building. Anakin calls in a gunship for immediate evacuation before leading his squad to assist Obi-Wan. They escape to the roof, and the droids follow them. Their gunship arrives, picking them up, but not before taking the command tactical droid's head to find out how the Separatists discovered their plan.

At the base, Rex and Cody analyze the droid's memory, but the best they can find is that the Separatists discovered their position ahead of time. Obi-Wan suggests that they may have a spy in their ranks. The Jedi decide to go behind enemy lines to investigate, while Rex and Cody sweep out the base. As the Jedi leave, Cody notices that someone left his comlink on, meaning the spy was eavesdropping on them. They spot someone running off and chase him. Unfortunately, they lose him in the mess hall, among their many brothers, meaning that one of the clones is a traitor. They decide to contact the Jedi. Unfortunately, the droids are keeping the communications jammed. Commander Cody and Captain Rex examine a severed tactical droid head.

As Anakin and Obi-Wan race to the Separatist base on BARC speeders, they notice an increasing number of droids spying on them, but still decide to continue the mission, despite the fact that it has been compromised. They arrive at the enemy base and inside, they meet Asajj Ventress again and begin to duel with her. Rex and Cody have R2-D2 analyze the communication history, to find out if anyone had sent out any unauthorized transmissions. Rex notices an irregular wavelength that is too low and infrequent for them to normally detect.

The transmission seems to be coming from Slick's barracks, so they decide to investigate. They question all of his men: one clone was cleaning his weapon, two were in the mess hall, and another was in the infirmary. The last one, Chopper, appears that he is hiding something, and reluctantly reveals that he was collecting droid fingers, which is forbidden by protocol. He denies being a spy, and Slick offers a full investigation when the Jedi come back. However, Chopper snaps that from his hiding place, he saw the clone turn into the command center rather than the mess hall. Cody also notes that he somehow knows about the Jedi's departure, while only Rex and Cody knew about it. Knowing he's been discovered, Slick punches Cody and Chopper, and escapes. Cody and Rex try tracking him, but they are too late: he blows up many of the gunships and AT-TEs, as well as the weapons depot, with earlier-placed charges. The other clones inform Cody and Rex that he went into the command center, and they order the others to secure the perimeter while they go inside.

Meanwhile, the Jedi defeat Ventress and demand her surrender, but as they edge closer to capture her, she creates a large hole in the floor beneath their feet, pushing them one level down. Ventress taunts them and runs away, and the Jedi follow her, discovering that she has set up a whole army to invade Christophsis. The Jedi engage Ventress again.

Rex and Cody enter the command center in search of the traitor. They look up at the vents (where he is hiding) and inconspicuously act out a scene. Cody leaves his blaster on the table while Rex goes to "secure the lockdown". Slick comes down from the vents and grabs Cody's blaster, only to find that it is empty, and Rex comes up from behind him and puts his blaster at his head. He engages the two commanders in physical combat, stating that he was tired of all the suffering and was offered freedom and money from Ventress. Cody manages to knock him out and they apprehend him. As they present him before the Jedi, the latter ask why he would betray his brothers; he snaps that his brothers are enslaved by the Jedi, that he was striking a blow for all of them, but they are too blind to see it. Cody and Rex reprimand him that if Slick truly loved his brothers, then he wouldn't have put them at risk. Cody orders the other clones to take the traitor to lockup.

Obi-Wan asks if they managed to salvage anything from the weapons depot. Rex says that though most of their weapons are trashed, they managed to save the heavy cannons, which will prove to be useful in the coming battle.

Trivia

 * This episode is a prequel to The Clone Wars movie. As the series progresses, it will become evident that some of the stories are more in the format of an anthology, jumping about the timeline. This is especially true of the second season of Clone Wars.
 * In the script, the opening sequence was to involve the clones setting up their own combat droid that they had nicknamed "The Beast." Its design would resemble the dome-shaped mining droids from Star Wars Episode IV: A New Hope, but modified with weaponry to look not too dissimilar to the head of a Dalek from Dr. Who. Ultimately, it was decided to keep the sides clearly defined as clones versus droids, and not clones using droids versus droids. Furthermore, the opening scene would not even display just what "The Beast" would do, so it was cut as an unnecessary story complication.
 * The script describes Obi-Wan's placement in the towers as both on 287th floor and the 46th level. This is not necessarily a contradiction.
 * Due to late editorial changes, at the end of Act I, you can hear Obi-Wan refer to Cody as both "Commander" and "Captain". The latter shot was originally of Obi-Wan referring to Rex.
 * During the first footchase inside the Republic base, it may sound like Cody orders Rex to take the left corridor (who then proceeds to turn right). What Cody actually says is "You take the west corridor."
 * The music that accompanies the brawl between Rex, Cody and Slick is a variation of the speeder chase from Star Wars Episode II: Attack of the Clones. Much of the background music consisted of an edited version of the "Battle of Christophsis" track from The Clone Wars soundtrack
 * Originally, Sergeant Slick was supposed to have red hair, but when rendered, the standard dark hair model was used. This actually helps him blend in more rather than stand out as a suspect.
 * Clone pilot Hawk was originally in the Clone Wars movie, called by Anakin for an extraction from the B'omarr monastery on Teth. That sequence was cut from the movie.
 * The clone barracks include pin-ups of Twi'lek girls and Naboo handmaidens.
 * Aurebesh translations:
 * Sketch has an Aurebesh "S" tattooed on his brow.
 * The side of the tactical droid's head is stenciled with "TACTICAL".
 * The display screen that Cody uses to contact the Jedi say: "SENDING," "RECEIVING" and "LOCATING STATUS".

Goofs

 * At the beginning of the episode, when Cody and Slick return, Cody is carrying a plain white clone helmet. He is seen holding his rightful helmet later on in the episode.


 * Just before the end Rex is wearing a pauldron with a different pattern on it.