Going Under (2004)

Peter, a married psychotherapist, and Suzanne, a professional dominatrix, have been engaged in an affair of sensual dominance and submission in an S&M dungeon where they must abide by the rules. Now, those rules are about to be broken when they agree to see each other on the outside.

As Peter becomes increasingly obsessed with the troubled Suzanne, they embark on a sordid psychosexual journey into their tortured pasts through their most carnal desires.