Last Breath (2010)

Tina Johnson and Michael Johnson have a son, Caleb, but they live an unhappy marriage. They are distant to each other and Michael has a love affair with his secretary Sarah. One night, Tina and Michael buy a derelict building that Michael expects to fix to make money. While showing the large space to Tina, they are surprised by a sadistic stranger and are tortured along the night. Who might be the stranger and why is he doing this to the couple?