Bugs tag
They've worked some weird cases (more so than usual) since Sam's return but fighting off bugs has to be one of the weirdest. Dean's not entirely sure what's going on but wondered if it had to do with their dad's disappearance. So much shit has gone down since then and it's only ramping up.
He wished Sam would let up on John, though - he wasn't perfect (nobody is) but he tried his best to raise them. Revenge just took over their lives. Dean desperately wants Sam to stay and is terrified he's going to lose him again. That can't happen.