The Doctor's expression darkens at her story. So that probably explains why poor Nimitz tried and couldn't make that full connection. They shouldn't have to have gone through that, the Doctor thinks, but she seems to be trying to be as matter of fact as it as she can. It's probably a military thing, but he can't miss the way she swallows or how Nimitz leans into her hand, as if he's trying to comfort her.

"I do. But I'll have to say, you're the first treecat I've met," the Doctor tells Nimitz. His eyes flick to Harrington. "Have you popped by Medbay?"

He's of course willing to help, but it's still something worth asking. He had assumed a military woman like Harrington would have wanted to get a "real" professional opinion, as rubbish as the Doctor finds those half the time. Then again, the Doctor is starting to come to the realization that he's wrong about several things about Harrington and it's probably high time he stops trying to assume she's standard military.