|"The Hidden Enemy"|
|Airdate:||Feburary 6, 2009|
- "Truth enlightens the mind, but won't always bring happiness to your heart."
Anakin and Obi-Wan discover evidence of a traitor amongst their ranks while attempting to lead Republic forces to liberate the planet of Christophsis from a Separatist siege. When the Republic is ambushed on Christophsis, it becomes clear that someone has set them up. The Jedi suspect the Sith, while Rex and Cody uncover information that points to a spy amongst them.
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 before the head malfunctions 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 and tell the clones to keep the mission classified. Rex and Cody then sweep out of the base, but as the Jedi leave, Cody notices that someone left his comlink on, 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, but the droids are keeping the communications jammed.
- Anakin Skywalker
- Asajj Ventress
- Obi-Wan Kenobi
- Unidentified Tactical Droid (Christophsis) (First appearance)
- TJ-55 (First appearance)
- Hawk (Helmet only)
- The script originally dictated the start of the episode to involve the clones setting up a combat droid nicknamed "The Beast", similar in design to the dome-shaped mining droids seen in A New Hope. However, to keep the war defined as clones vs. droids and not clones using droids vs. droids, and since the sequence didn't even explain the droid's use, the sequence was cut.
- 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.
- During the episode, Chopper's right eye changes color. When he is first cast under suspicion, his right matches his left eye's brown color. Later, however, his right eye is an off-white color.