Calvin smirked, both disappointed and relieved that Katie had pulled away, but not at all unhappy that she'd reacted. He hesitated before following her, trying to get his thoughts under control. Then he gave up; thoughts never hurt anything, and he wasn't high on self-control lately anyway. What was the point? Whatever was going to happen would happen.
"Thanks," he said. "That's great." Yeah, just saying the first generic thing that popped into his mind. At least you couldn't say he was flirting, he was being too inept for that. "Thanks for helping me out."