I think Daryl thinks Beth's disappearance is on Daryl. That was why he spent all night running and trying to track them. His collapse is both physical and mental. Everytime he starts to care about someone, he loses them. It will be interesting to see if Daryl ends up joining that new group and killing anything and everything.
I don't remember the character name, but the actor is Jeff Kober. Anyone else think it was his group that took Beth? I thought so initially, but not so sure now.
Was at least part of that group in the house with Rick and Coral?