When Trish arrives home one night to find the lights on and a stranger waiting at her bedroom window, she runs straight to her neighbor Liz’s house for help. Though they haven't spoken in years, Liz invites her inside, but Trish immediately feels something is wrong. The more Trish learns about how Liz and her son Nathan have been living, the more certain she becomes that a threat to all their safety is quickly closing in around them.