I don't think it's anything you did.

[He can't think of anything that could cause Teddy to willingly change like this so suddenly; he'd almost died a few times while they've been here together, between the Skrull attack and the zombie draft, and Teddy didn't get this clingy in the aftermath. They'd kept close, sure, given each other reassurances and staved off the terror that comes from nearly losing a loved one. And Teddy had more reason than most to fear that, after everything he'd already lost.

But this... the possession surely couldn't have frightened him so badly that it caused him pain when they were apart, a pattern Billy had begun to recognize days ago and initially dismissed as nonsense. With the evidence right in front of him time and again, it's impossible to ignore now. And if Teddy doesn't realize what's happening...

...well, there's one way to make it clear. Billy's expression grows serious, and he starts to lower his hand.]

Teddy... what would you do if I had to go away for a while? And you couldn't come? How would you feel?