At the Mercy of a Stranger (1999)

Elizabeth is married to Thomas, a prominent doctor. He has been abusing her. One day while out with a client named John Davis, he tells her that he was hired by Thomas to kill her. It seems that she wants a divorce and Thomas would rather see her dead than let her leave him. Now John observed her before actually doing it and discovered that she was not the woman Thomas described, so he decides to help her. He wants her to pretend to be dead so that when he gets his payment, he could get Thomas to incriminate himself on tape. Though uncertain at first, she realizes that he is telling her the truth. But she finds it unbearable to be away from her children and Thomas doesn't pay John right away. So she has to pretend to be dead longer than expected.