Jessica Chambers confronts her husband John about having an affair with one of his students, Vivienne Ballard. John agrees to Jessica's demand that he immediately end his extramarital relationship. To repair the animosity in their marriage, John also agrees to a family vacation at a remote plantation house with their 14-year-old daughter Anna.After settling in, Jessica instructs John to purchase veal cutlets for dinner despite John preferring hamburgers. At the store in town, Anna takes an interest in 18-year-old local Isaac, who flirts oddly with Anna. The store owner, whom Isaac identifies as his Grandpappy, eyes John suspiciously when he tells Anna he couldn't find veal, even though the store carries plenty. Grandpappy writes a note on John's receipt that reads, "You are being watched by the devil."When they return to the house, John and Anna find Jessica trying to open a locked door to a mysterious room. The family is unable to get inside.Isaac comes to the house to invite everyone to dinner with his Grandpappy. Jessica learns John lied about having to buy hamburger meat when Isaac says they will be cooking veal since their store has so much of it. To spite her husband, Jessica agrees to the dinner invitation.Upset about having dinner with strangers, John shows Jessica the worrisome note on his receipt. John and Jessica have a fight about the veal that leads into a bigger argument about their marriage. John and Jessica eventually reconcile after John swears he ended his affair with Vivienne.John and Jessica decide not to go to dinner after Anna suffers a sudden nosebleed. However, Isaac unexpectedly returns with his Grandpappy and offers to cook there. Although suspicious of Isaac's motives, Jessica reluctantly allows the two men inside.While Grandpappy cuts carrots in the kitchen, John asks him about the note he wrote on the receipt. Grandpappy cryptically says that when men do bad things, they sometimes open a door.During dinner, Jessica's concerns grow due to Isaac's bizarre behavior, flirtation with Anna, and the way he seems to already know his way around the house. Isaac also performs apparent magic tricks, including lighting candles with his finger and later producing a key out of thin air. As the tension between everyone builds, Anna faints from a sudden nosebleed. Isaac becomes more aggressive when Jessica and John demand that he leave. Anna's cat Toby inexplicably becomes trapped inside the locked room, which further escalates the family's terror.While Isaac supposedly uses the bathroom, Grandpappy tells the family he isn't actually Isaac's grandfather. Grandpappy claims he decided to take in Isaac after he mysterious appeared from the swamp one summer. Grandpappy also claims Isaac doesn't age.Grandpappy proposes playing music. Inexplicably, the record he chooses plays a recording of a private conversation in which John promises to divorce Jessica while professing his love to Vivienne. Jessica realizes John lied about ending his affair and had no intention of saving their marriage. To deflect the unwanted attention on him, John makes a claim that Jessica must be participating in a plot with the two men to torment him.Isaac reenters the room with Anna's cat safely in his arms. Jessica and Anna spot an unknown animal outside. The family becomes even more uncomfortable when Isaac retrieves a shotgun that he threateningly uses to further heighten their fear.John agrees to go outside with Isaac. Once they're alone, John reminds Isaac that he hired him to kill Jessica and to make the home invasion look like a robbery. John demands to know what Isaac is playing at by going off script with voodoo illusions and the recording of his conversation with Vivienne. Isaac agrees to go back to John's original murder-for-hire scheme.Jessica tells Grandpappy she believes Isaac is evil. Jessica bargains to leave John behind if Grandpappy agrees to let her and Anna leave, but Grandpappy refuses the offer.John and Isaac come back inside. Despite promising to follow John's plot, Isaac turns the tables by locking John inside the mysterious room instead of shooting Jessica.Vivienne shows up at the front door saying she received an urgent text from John. Jessica quickly explains what is happening and instructs Vivienne to go to the police. However, Vivienne discovers her car will no longer start and she is now locked inside of it.John demands to be let out of the locked room. Isaac tells John to open the closet door. When he does, a wolf attacks John.At gunpoint, Grandpappy escorts Anna outside and threatens to shoot her mother unless she pours gasoline all over Vivienne's car. To spare her daughter the trauma, Jessica pours the gasoline instead. Grandpappy sets the car on fire and Vivienne dies. Jessica uses the explosion as a distraction that allows her to beat Grandpappy to death with a hammer.Jessica goes back inside the house to find the wolf mauling her husband. With his dying breath, John asks his wife to tell Vivienne that he loves her.Jessica returns outside to find her daughter held hostage and Isaac proposing that he will run off with Anna. Isaac explains that John hired him to kill Jessica, but he decided John deserved to die instead.Jessica wrestles away the shotgun and uses it to shoot Isaac. As he bleeds out on the ground, Jessica asks Isaac who he really is. Isaac claims he and Grandpappy built the house centuries ago for sinners like John, and it is their task as moral compasses to kill the wicked. Isaac coyly adds that he could be a demon, an angel, or just a confused kid.Jessica and Anna escape in their car and drive to a sheriff's station. After hearing about the ordeal, Deputy Torres tells Jessica that there isn't a house at the location she described. Jessica insists that she and the deputy go there together. Upon returning to the property, Jessica is shocked to see that the house and the bodies inexplicably disappeared.On their drive back to the station, Torres instructs Jessica to open her patrol car's glove box. Jessica finds a video camera from the house whose footage shows Isaac asking Jessica to turn around. When she does, Jessica sees Isaac and Grandpappy driving by in their red pickup truck.Torres tells Jessica that Isaac and Grandpappy aren't human, but they help keep order by sending evildoers to Hell. Reminding Jessica that no one will believe the truth if she tries to tell it, Torres advises Jessica to embrace the second chance Isaac gave her and to never return to the house on the bayou. Torres throws the camera out the window and it bursts into flames. Jessica reunites with Anna back at the station. (thanks to culturecrypt)