Star Wars: Clone Wars Season 7 Episode 2 - 3 Ups & 3 Downs
2. Up - Echo The Winter Soldier

The final big twist of the episode (that everyone surely saw coming) is that Rex was right, and Echo was the one providing the Separatists with their algorithm.
In the episode's last few minutes, the clones find Echo alive in a cryochamber, a la The Winter Soldier from the MCU. Rex and Tech free him, and, though he's a little out of it, he and Rex have a nice reunion.
The best part of the reveal is just how ominously peaceful it is. Echo is safe...for now. His long captivity is definately going to come back into play later in the season, and Clone Wars brilliantly and horrifingly asks us how.