Doc stops walking with the tools and then gives her a look, with a carefully raised eyebrow as well.

He's not quite sure what to say, at first.

"Now that wasn't part of the deal," he protests. That's just not fair! He crosses the room and sets the tools on the nearest desk, still looking at her. "It ain't...you don't gotta help, Kate, I'm supposed to be repayin' you for all this!"

It's a weak protest at best, because Doc realizes that she's got him beat.