Inside (2006)

"Inside" is a 2006 Drama movie directed by Jeff Mahler and starring by Nicholas D'Agosto, Cheryl White. Alex has a disturbing hobby of following strangers...until one night he gets caught. Instead of calling the police, the couple--fascinated by Alex's resemblance to their dead son--asks him to stay, and Alex finds himself trapped in a horrifying existence of desperation, despair, and insanity.