So like all good whodunits, half the fun for me is figuing out the mastermind. So I'm saying straight up - right now, it's gotta be Barriss. Place money on it, I'm that sure. Lets take a look at my reasoning: For starters, we get the text at the beginning: Never become desperate enough to trust the untrustworthy. On the surface, you'd think "Ah - this is talking about Ventress". But she played it straight with Ahsoka, didnt betray her and was more or less on the up-and-up the whole episode through. So take her off the table. Does it refer to Barriss? And then there's the form of the mysterious - slender and undenyably female. And of course last week, there's her reaction to the information that Letta was in Republic. Ahsoka gets pissed but Barriss tells her not to worry, that the evidence is clear, and that "nothing will ever change." Her reactions and body language (well, as best you can read it in a cartoon) says that she has something on her mind. Lastly - and most damming - who else could it be? Every viable suspect is above reproach (The Big Name Characters), dead or added in at the last moment (Ventriss). By process of elimination based solely on screen time, it has to be her. Three episodes into the arc and no other likely suspects.