Tick Tock (2000)

Beautiful Rachel is the homebound wife of a wealthy, emotionally cold millionaire, Holden. While Holden is away on one of his many business trips, Rachel's close -- very close -- friend, the equally beautiful, plots to kill Holden for the inheritance. With murder on their mind, they seduce simpleton cowboy Travis, whom they meet in a bar, and convince him to do their dirty work. Meanwhile, unbeknownst to the cunning women, a private eye hired by Holden to follow Rachel (he suspects her of having an affair) discovers the scheme on the night of the intended murder. Alibis backfire, loyalties are questioned, and more than one murder takes place before the unpredictable ending.