She isn't freaking out, but S-4 is talented enough at reading souls that he can see the way her very essence stutters at the mention of Dr. Watts. He doesn't get scared, though, just a little shocked. Whoever this is must really care about that man...

"Um, I don't know. I don't really know where he is. Sans does, but..."

But he's not really in the best condition right now.

"I-I can help you look for him, though!"