(Note: portions of this synopsis are told in chronological order to eliminate confusion)In the opening credits the audience is told the story of a group of teenagers whom performed a satanic ritual in a rural Louisiana home in the 1980s - causing one of the teens to murder the four others and then commit suicide.In the present day an elderly man is sent to investigate the long abandoned home after his wife claims to have heard strange noises coming from the property. After he does so he calls the police and Detective Mark Lewis is dispatched to the scene despite his plans that evening to have wine and dinner with his girlfriend police psychologist Dr. Elizabeth Klein.Entering the house, Lewis discovers the dead bodies of three individuals - brutally murdered with an axe - and discovers a fourth in the upstairs bedroom who turns out to be still alive. Taking the survivor from the scene, the young man (named John) begins to recount the occurrences leading up to the murders. As Lewis launches a homicide investigation he calls in Elizabeth to handle John's interrogation - unsure if he's a victim or the suspect.John recounts events from a week earlier when he was interviewed by his girlfriend Michelle and her brother Sam regarding visions he was having of his deceased mother sitting in a house he didn't recognize telling him to "let go". Michelle and Sam, as it turns out, are a part of a amateur ghost-hunting team consisting of themselves and three others: Paul (Michelle's jealous ex-boyfriend and leader of the group), Jules (the team's expert on spirits and occult knowledge), and Donnie (a quiet tech guy). Michelle and Sam insist that if they can investigate the location within which John's mother appears in these visions he can gain some closure, sleep better, and stop having them altogether.Days later when the team deduces that the house in John's visions is none other than the same one that the satanic murders took place in the 1980s, the group heads off to investigate - John reluctantly coming along. Tensions are high between Paul and John during the ride there and when the team begins to set up all their equipment. As strange occurrences begin to happen, John somehow reveals the location of a large circular design hidden under a rug. This design turns out to be the seal that was used in the ritual performed in the '80s, used to summon and communicate with the spirit world.Later on when a painting suddenly bursts into flames John runs to fetch a fire extinguisher from a nearby closet and puts out the blaze. The team realize once again John inexplicably knew where something was and tests his knowledge of the home - John somehow knowing the location of a drawing of a girl underneath some wallpaper and an image of the seal imprinted on the back of a photograph. Jules is suddenly pulled across the house by an invisible force and when the group recovers her John insists that they must leave the house before something worse happens. Both Paul and Jules rebuff this, explaining that this kind of evidence is what they've been searching for as ghost-hunters and recording/sharing it would not only be ground-breaking but would legitimize their choice of work.A distressed John continues to try and convince Michelle to leave but the two are approached by Paul who reveals that he discovered that John's mother was not only present in the house the night of the murders in the '80s but she was also the only survivor of that night. Paul explains that if they stay and perform the seance then perhaps John can communicate with his mother and figure out what she's trying to tell him - putting her soul to rest.The group uses the seal to perform the seance and as an increasing number of paranormal things begin to occur around them Jules repeatedly reminds everyone to not "break the circle" by releasing the hands of those on either side of them. During the chaos and confusion, Michelle begins to experience severe pain and John sees his mother next to him - telling him to let go. When John lets go and breaks the circle to aid Michelle things turn for the worst and the group scrambles away in different directions - John eventually coming across Paul who's standing in front of a painting repeating over and over that he must kill everyone in the house. Paul attacks John, who manages to escape, and Paul disappears into the darkness.Back in the present, Dr. Klein continues to grill John about what happened in the house - uncovering that Michelle is ten weeks pregnant - while Detective Lewis tries to piece together events from physical evidence and what they can find on corrupted video recordings. Eventually, Lewis deduces that the three dead bodies belong to Sam, Jules, and Donnie and that Michelle and Paul are nowhere to be found. Given the information that John has provided up to this point, Paul appears to be the killer and he may have fled the house in pursuit of Michelle. When a stolen vehicle report comes in from nearby, Lewis puts in APB out on the car which is soon found, crashed, not far away.When police officers approach the overturned vehicle they find a badly injured but alive Paul but no Michelle. Paul suddenly awakens and injures one of the officers, takes his gun, and flees into the woods - eventually making it to a convenience store where he assaults the cashier and quickly becomes cornered by the police.Lewis goes to confront Paul at the store and has his officers slide a walkie-talkie through the door - hoping to negotiate. When John hears what's happening over Dr. Klein's radio he grabs it and begins yelling and threatening Paul - demanding to know where Michelle is. When he hears John's voice Paul picks up the walkie-talkie and begins screaming into it over and over. On the other end, John flies backwards and begins to have convulsions as he goes into cardiac arrest - the convulsions getting worse each time Paul screams into the walkie-talkie. Dr. Klein pleads with Lewis to do something to stop this and the detective fires three rounds into Paul's chest.As Lewis leans over a dying Paul he asks him where Michelle is to which Paul responds by grabbing the cross necklace around Lewis' neck before succumbing to his wounds. One of the other officers then points out that the reason Paul wasn't communicating with anyone was because he had had his tongue removed.Returning to the house, Lewis enters the bedroom where he first discovered John and goes into the walk-in closet which held a box of crucifixes he had noticed before. Exploring the closet, Lewis finds a small hidden door into the interior of the house where he finds a bound and gagged Michelle. As she's being helped away by paramedics she repeats "same room" over and over to Lewis.Between interviews with John, Dr. Klein conducts research of her own and discovers that the seal used in both the past and present seances is called the "Seal of the Left Hand Path" and is intended to release a demon from its prison by possessing someone involved in the seance, murdering the others, and then committing suicide before transferring to a "pure vessel" and being reborn into our world.When Dr. Klein's attention is brought to footage just un-corrupted from the house she sees that it was in fact John who was standing in front of the painting repeating that everyone had to die, not Paul, and further footage shows him attacking Paul and removing his tongue before murdering Jules, Donnie, and Sam.Dr. Klein goes to confront "John" with this revelation who tells her it's too late and that he will be free before an invisible force begins to choke her. Lewis suddenly enters the room, having found the real John's dead body in the same room where he found Michelle - having committed suicide by hanging. As Dr. Klein is released by her attacker, "John" disappears into thin air as Michelle is moved across the seal on the floor of the house. Dr. Klein frantically views the footage from the camera which had been recording her interviews to find that "John" doesn't appear anywhere on the recording.As Michelle is transported away in an ambulance she tells the paramedic that she felt a kick from her baby. The paramedic checks to make sure that the child is alive and healthy and confirms as much. The film ends with the now demon-possessed child moving around in Michelle's womb...