Table for One (1999)

Matt Draper is a man who lives two lives. In one, he's a prescription salesman living in a rural country house married to an emotionally withdrawn young woman, named Ruth whom he keeps locked up within the house, as more or less a prisoner. But as Dr. Matt Swan, he regularly commutes to nearby Los Angeles where he's a wealthy pharmacist married to a wealthy socialite named Ariana Harpwood and has two children with her. Neither wife is aware of Matt's double life or his unwillingness to let either one go. When Ruth becomes more unstable when she suspects Matt is cheating on her, she starts a romance with Tom Bernard a married neighbor who moves into the country house just next door. When Matt realizes that Ruth is socializing with people, (against a stern rule he gives her) he plots to get rid of her, unaware that Ruth is plotting to do just likewise, but she's unaware of her new friend Tom's dark secrets.