Faithful (1996)

Margaret O'Donnell thought she was the target of her husband's affections. She was only half right. Inside her sprawling Westchester mansion, Margaret talks on the phone to her husband Jack, who makes excuses for being late coming home on the evening of their 20th wedding anniversary. A brief scene with his gorgeous assistant Debbie makes it clear that he has other things on his mind than his marriage. Depressed and contemplating suicide, Margaret slips into a bath, while video monitors reveal that an intruder is stealthily breaking into the house. He turns out to be a hired killer named Tony whose first rebuke to Margaret--after he's tied her up--is, "You should have been faithful to your husband." Tony has been hired by Jack to eliminate Margaret when the telephone rings twice, signaling to the assassin that Jack's alibi has been established. In the meantime, a game of seduction ensues as Tony helps Margaret regain her self-respect, and she helps him confront his own demons.