"Uh-huh." That has some implications he's not sure he wants to consider, even if he has been acting like an overprotective dad towards Casey. And he worried about Casey while he was gone. And- nah, he's not going to consider it as a possibility right now. The fact that Casey was just gone for two years takes precedence.

Speaking of which: "The Fugitiods," Wash repeats slowly. "I don't think you've mentioned them before." And because it's worth asking outright: "What happened, anyway?" Between new aliens and time travel, there's a story to be told there.