The Hidden Enemy Star Wars: The Clone Wars : Season 1 Episode 16

Anakin Skywalker and Obi-Wan Kenobi lead Republic forces in an attempt to defeat the droid armies and free the planet of Christophsis from the Separatist siege. When the Republic is ambushed and forced to retreat, it becomes clear that someone in their midst has set them up. The Jedi believe this infiltration is a Sith-backed operation and go behind enemy lines to investigate. Meanwhile, Captain Rex and Commander Cody set out to uncover the traitor amongst them.