Set before the events of the theatrical Clone Wars movie, "Hidden Enemy" is an excellent companion piece to the film. (And in some ways, even better.)
As the Jedi plot a decisive rout of Separatist forces on the industrialized planet of Christophsis, their plans are foiled by a traitor in their midst. After luckily fighting their way through their trap-turned-hostile-ambush, they realize that a simple security breach couldn't have turned the tide as badly as all that.
They decide more answers might be found if they gather information at the Separatist headquarters, leaving Cody and Rex to investigate the troops.
But it's all a trap. Ventress is waiting at the Separatist headquarters in order to occupy the Jedi long enough for the traitor to blow up as much of the artillery and armoury as he can, thus leaving the Jedi in the horrible strategic position we find them in during the events of the film.
All in all, another generally good episode. Interactions between the Clones were interesting to watch, though I wish they would have elaborated a little bit more about his motives other than having him shout, "I'm sick of being a slave." The lightsaber dueling was top-notch and I like it when they're able to fit one into the the episodes with Jedi. Ventress has a good way of using her arrogance and over-confidence to her advantage and I'm not sure if it's an accident or not.
The best stuff in the episode, however, was the investigation by the Clones. I mean, there isn't a whole lot of interrogation and red-herring planting you can do with half of the story of two-thirds of a 28 minute show, but I think the writers did everything they could to make it interesting to their story, their audience, and their time-frame. I would like to see more episodes just about the Clones though, without the Jedi around, I think they can be far more interesting that way. In fact, "Rookies" was probably one of the most well-written episodes of the series.
I also really enjoyed the musical arrangements in the episode. One of my favorite pieces of music from Attack of the Clones (the speeder chase over Coruscant) was used to thrilling effect when the clones were in the midst of a fist-fight. Normally it's hard for me to separate a piece of Star Wars music out from it's original cues, but here it fit so well I almost didn't notice it.
As for next week, we're looking at an hour long installment about biological-warfare on Naboo. You can see a preview of it here. The action looks really cool, my only real complaint is Jar Jar's voice. I never in a million years thought I'd miss Ahmed Best's performance but it sounds like his replacement on the show isn't even trying. Can somebody tell me what else Ahmed Best has got going that he can't come and make Jar Jar more bearable?
So, until next week.