[It's not that Wendy doesn't believe him, it's more like she's seen this symptoms countless times before in test subjects and sacrifices alike. So she's viewing all this with a heaping scoop of skepticism. She's a scientist. It's what she does.]

Can't say you don't know. I won't be able to give you anything if you don't give me an idea of what could be in your system right now. [A slight chuckle, maybe a bit nervous-sounding?] You really don't want me going with a random guess.

[She shakes her head.] I don't think you're crazy. I think this is just a response to something I haven't identified yet. [A pause.] Do you wanna walk? We can walk. [And she gestures towards back from where she came, her other hand gently touching his arm.]