Voyeur on LetMeJizz
Watching someone who has no idea they're being watched is the entire hook, which is what separates it from exhibitionism, where the performer plays straight to the lens and wants the attention. The frame here pretends to be an accident, a gap in a curtain or a fixed angle catching a couple who never broke character for a camera. That stolen-glance quality is the whole charge, the sense of seeing something not meant to be seen.
822 voyeur videos here, all HD and all free. New ones go up daily, so check back if you don't find your scene first time around.