[Stan does not let go. The most he does is lower Sif a little bit so the hold doesn't pull on his neck quite so much. His heels can fully touch the ground, as a treat.]

Relax, relax. I've only got one more question, and if he can talk his way outta this one he might be in the clear. Maybe.

[Maybe they're all expecting Stan to ask something more obviously relevant to the case, maybe if he rooms with anyone or who saw him last. But no, instead--]

Pop quiz! Why do you have to develop pictures in a dark room? If Dipper was showing you how photos work, then he must've warned you the doors and windows gotta stay shut. How come?