Open House (2010)

A couple on the verge of a nasty divorce attempt to sell their empty love nest and move on with their lives, separately. After a successful open house they are horrified to discover, days later, that a potential buyer didn't leave their home. While Alice is being held captive in the basement, the unannounced house guest moves in upstairs. She senses her capture is being kept a rebellious secret. She knows her way out, if only she can get out alive.