The Lost Woman (2009)

On a camping trip, Dora disappears. While friends search for her, Dora's husband Spencer and best friend Lydia discover they are attracted to each other. Their friends notice and become suspicious. The detective, Michelle Tierney is convinced that Spencer and Lydia are guilty as Dora has life insurance worth two million dollars and Spencer is one million dollars in debt. As it turns out, Dora ran away and had been staying with a friend. Upon her return, she becomes suspicious of Spencer and Lydia's affair. Dora confronts Lydia. They argue and Dora falls down a staircase to her death. Spencer and Lydia are prime suspects in conspiring to murder her. Tierney is determined to bring them to justice. She spearheads the filing of a criminal complaint against them. She finds out that Spencer's first wife committed suicide and he might have been responsible. Tierney also shows Lydia pictures of Spencer with another woman and implies he may be using Lydia. Lydia confronts Spencer. He tries to convince her she is the only one he really loves. The case is dismissed because forensic evidence proves Dora fell. In the last scene, Spencer admires the two million dollar check. Lydia's tells Spencer the forensic results were wrong and that she pushed Dora. She says she did it mostly because she didn't like the person Dora had become. Lydia asks Spencer if he knows how angry she'd be if he were unfaithful to her? Her response leaves Spencer in disbelief.