BETWEEN THE LIES (1997)

A private detective has an affair with an obsessed client. She then starts putting ideas into his head that his wife is cheating on him with her dance partner hoping he will leave his wife for her. The private detective then thinks that his wife is actually having an affair and starts spying on her and ends up having an affair with his client again thinking it is OK because his wife is cheating on him when she is actually completely innocent.