A teenage boy returns after being missing for months not remembering what happened to him or that a murderous demon has come back with him just in time for a killer 18th birthday party.

SYNOPSIS:

In the affluent Lake Forest, college student Elijah is taking his younger brother to a horror movie finally fulfilling a promise he made to Liam some time ago. The film is now playing only at a cut rate theatre in Chicago, so Elijah uses this as an opportunity to stop and pick up some weed at a dealer’s place in a sketchy South Side location. Elijah makes Liam wait in the car to hide the nature of this visit. Waiting, a restless Liam gets out of the car to stretch his legs only to be quickly pulled into an alley. When Elijah emerges and finds no Liam he tries calling his brother’s cell phone only to find it ringing smashed in the alley. He also finds Liam’s bracelet and realizes Liam hasn’t left of his own volition. He calls his family to tell them the horrific news. His father Noah calls the police.

Detective Price questions the family if Liam could have run away or had a secret life, but they insist he was an innocent happy boy. Price asks if Elijah could have had a disagreement. Their sister Amelia points out that Liam worshipped Elijah who was always there for him. Their father comments, except this time. Their mother Sienna expresses her disbelief that Eli would do something so stupid. Price points out the disturbing reasons why someone might have snatched a 16 year old boy. Cut to a flash of Liam screaming in the woods.

As the months drag on with no sign of Liam to the family but glimpses of him frighted in a basement, being abused show what is happening to him. Noah shows up at the police station to rant to Price as to why there has not been a single clue to Liam’s disappearance. Price counters with they had just found the body of a teen boy, but it wasn’t Liam. As Elijah’s guilt is overwhelming him, a moment of Liam clean, dressed nicely and suddenly looking diabolical comes on screen. As the family finally, regrettably moves on, Liam’s school even has a memorial assembly. The demon transformed into the body Liam is all over the place viciously murdering people right and left just for the fun of it all. Liam is now being controlled by a demon using him as a vessel for the violence he enjoys. At once point he collapses and the weak, distraught teen Liam emerges for a moment. The demon fights him for control of his body.

Later at the far side of Chicago a practically catatonic Liam is stumbling down a street and passes out after narrowly being hit by a car. A traffic cop sees this happen and calls in a probable drug overdose but recognizes Liam from missing person’s bulletins. He calls Price. With Liam in an ambulance on the way to the hospital Price calls Noah to say that they have found Liam and he’s alive. The family rushes to the hospital to find a broken, malnourished and sexually assaulted boy who recognizes them but remembers nothing of his ordeal.

Back home Liam recognizes virtually nothing, even his house or where to find the bathroom. He is startled when the housekeeper Salma hugs him but when she gives him his favorite Gatorade he remembers who she is. While the family is happy to have Liam back he is not the same boy, while he has grown and gained muscle from some kind of physical activity, he never has anything to say to anyone and has no interest in any activity. He has violent nightmares but can’t remember what they are about. His brother says he knows that horrible things were done to him only to have Liam startle him by saying he knows he did bad things to people himself and he liked it. Eli suggests that Liam talk to Price about things, but Liam flips out refusing to even consider it.

One night in the bathtub the demon reveals himself. He has been there all along and has been rejuvenated. He is now ready for some fun. Liam pops up through the house watching Elijah in the shower, waking up in his sisters bedroom asking Amelia and her boyfriend Paul if he interrupted anything. He later wants to get into the sauna with Paul naked, but Amelia say that it isn’t acceptable. Glimpses of the multiple murders that the demon Liam has committed keep flashing quickly from time to time. Noah walks into his bedroom to get dressed to go out. Liam had been touching his mother’s underwear laid out on the bed. As Noah is getting dressed Liam asks if he is sexy and, unseen to Noah, is putting on his mother’s make-up. When Liam asks Noah to come to him seated at the vanity he embraces him with lipstick getting all over Noah’s shirt. Liam recalls having to wear make-up with some older man who would rape him. Noah, disturbed when Liam starts touching him, suggests Liam see a therapist which Liam angrily rejects.

Sienna thinks an 18th birthday party for Liam would be in order to try to bring him out of his shell. Liam is not interested but the demon takes over, thinking it is a wonderful idea. While Liam has not reconnected with any friends his mother has invited twins Iris and Ivy who have known Liam since 3rd grade. Elijah invites his girlfriend Amelia and a coworker Mia. Amelia brings her Paul and a gay co-worker Troy. Salma has prepared a feast for this sleepover party that ends with a birthday breakfast the next morning. Liam is fighting the demon but after midnight the demon goes into overdrive. Ivy and Iris are seduced by a nude Liam to get into a bubble bath where he throws in an electric blow dryer; Mia is thrown off the balcony. Troy is fried, locked in the sauna at the highest setting; Salma is bashed by dumbbells. A spear goes through Paul and Amelia in a two for one delight. Yvonne finds the twins and tries to shield Liam from the sight, but he stabs her telling her he has already seen them. Elijah finds Mia’s body and frantically looks for Liam who is in their parents’ bedroom. Noah emerges from his shower to find Liam in bed with Sienna. He tells daddy that mom has lost her head. Throwing Sienna decapitated head at Noah they fight, only for the demon to pretend the teen is back and strangle Noah. Liam passes out before Elijah finds their parents bodies. He plans to take Liam to the hospital and carries him to the car in the garage. The demon reveals himself and knocks Elijah out as the garage is filling with deadly exhaust. As the demon goes to Liam’s bedroom we see tears rolling down his face as his passes the mirror. Salma’s husband finds the bodies and Amir calls the police. Price finds a catatonic Liam bound and gagged in the closet as the demon, now in Amir’s body gleefully leaves the Billington’s house.