Speaking of Supernatural, it was explained that the first born son of the family was to be claimed by the demon (most likely crossroad demon) when the grandmother made the deal to be wealthy. That was the interest with Hunter. Not sure how a third movie could go down. Maybe surveillance cameras all though out the town or city.
My biggest complaint storywise, was why didn't they just call the cops when the really bizarre stuff started happening. They could have just rolled back the tape as proof. Or why didn't the mom and hunter just go with the daughter and dad to the vet. Totally could have avoided being possesed. What a dumb ass, haha.