Cas isn't always perceptive when it comes to nuances of human behavior, but he's depressingly good at reading Dean. He has the same look on his face that he had in the Lisa's hospital room, and when he'd walked away, a hand over his mouth, out of the hospital and down to the Impala. Cas had watched him go.

Bringing it up will hurt. It'll dig a knife into a closing wound, peel it open, expose something neither of them want to look at. "I'm sorry," Cas says, and that's all he says.