As it turns out, the "John" that Elizabeth was interrogating was the demon, who, as he begins to make Elizabeth choke, elaborates on the events that transpired – the seal the group found in the living room is what bound him to the house; John's mother was supposed to be the vessel of his escape, his possessing John, killing everybody and that he needs to cross the seal – in order to set himself free. The lights begin to turn on and off, and as Mark bursts open the door, he vanishes just as Michelle is wheeled out of the house.
