The most recent episode. I really enjoyed it, and would personally rate it up there with one of the better episodes of this series.
Things like the bonding scene between Rick and Carl really moved me (No, I wasn't in tears or anything, but you could feel their father/son bond).
But nevertheless, I can't wait for that next episode! He's back!
My hypothesis is, he will come onto the campus, where they will obvious point guns at him, and he will say something along the lines of him not having anything to lose anymore, so if killing him is what they feel is needed, so do as they wish. But yeah, I think they will team up with him (even though no one really likes him), and from there, they'll be set for the rest of the season, probably taking on the next bad guy, named Abraham or something (According to the comic).