It starts with that the guy and his GF/wife is short of money I believe, or they were just bored, and this rich guy offer them money if the GF/wife do some sex stuff with him. It escalates to full sexual usage of her. After that the BDSM comes into the picture with her put into one of those restraints and later into cage where she has to spend the sometime. The rich guy also told her that if she wanted, he would sell her on an auction as a slave.