Betrayed or abandoned by two of the most important folks in his life; having to realize and admit that he wasn't there for someone he spent so much time with before they died...
I'm guessing this is where we'll start to see the crucial difference in how Peter and Andy deal with adversity. I've never been sure if Andy's smile is a facade or indicative of a genuine ability to pick himself up and move on in life.
Interestingly enough, Mulligan's face in the last panel is more what I expected Peter's expression to be. Christo's reckoning has only begun, I think.
Oh and Peter's expression in the first panel was absolutely brilliant... The look on his face of sheer surprise and shock, it's like even with everything Christo has done, he still crossed a line Peter never expected he would.