Shrike hesitates to take the water bottle. It's not that he isn't thirsty (it's probably obvious that he is), but that he's still a little reluctant to take things for free. He feels like he ought to be giving something in return.

That, and the fact that Dimitri seems to think highly of this Grant person aside, what he's saying catches Shrike's attention.

"Therapy?"

He has absolutely no idea what that is.