Whirlpool (1970)

A blonde fashion model, Tulia is lured to an isolated country estate by a creepy older woman, Sara. There she meets Theo, orphan and homeless boy who has given a home by Sara. They call each other as aunt and nephew. He is photography-obsessed and even creepier than Sara. Tulia doesn't seem too perturbed to learn that a previous female model, Rhonda that went there has disappeared without a trace, nor does she find it strange that her first night there they get her drunk and engage her in perverse game of strip poker. She almost has sex with the boy while the old woman secretly watches but he isn't able to rise to the occasion. The next day he takes her into town and pays a friend to rip her clothes off and nearly rape her while he takes pictures. This doesn't seem to bother her either because soon she's involved in another bisexual three-way sex/photography session with them. There is also an allusion to the old Bluebeard story-the model has been forbidden to enter the boy's mysterious darkroom.