Paranormal activity opens to a woman pulling up to a house this then cuts to her husband setting up the camera. Once the lady is in the house it is apparent that she is spooked by her surroundings. Her husband questions her about her past and what she thinks is happening to her. This then is interrupted by the door being knocked, a priest enters, from him entering we know that he is going to exoricise the house. The priest quickly leaves telling the couple that the demon has to great a power to send back to hell. This is very effective as we now know that this demon is very dangerous and cannot be stopped. She then begins to tell the story of how she has always been followed by some sort of demon. This opening is very effective as from the start we know that something demonic is following her, we also know that the poltergeist is going to start to become more active as the husband starts to film the room as well.