When Aaron (Jeremy Sisto) and his wife Beth (Kate Ashfield) return home from a family holiday with their two children Marley and Max (Ryan Simpkins and Ty Simpkins), they discover that not only was their house broken into but the person had been living there, eating their food and sleeping in their beds. Shaken, they clean the house and make plans to install a security system. Distraught and traumatised, the family begins to notice odd occurrences around the house. The terror quickly escalates when they discover the intruder has been going through their personal items. Is this simply an after-effect from the crime, or is something else going on?