The film is about an 11-year-old boy named Eli (Charlie Shotwell), who's immune system is so weak that ordinary air can kill him, forcing him to live in seclusion for most of his life. His parents tell him that they have found an autoimmune specialist, Dr. Isabella Horn (Lili Taylor), who has a perfect track record for curing other children with his condition. The family drives out to an isolated medical facility run by Dr. Horn, but as things progress, Eli becomes convinced something is not right. The treatment seems to be making him sicker, and he's convinced that the place is haunted. He becomes suspicious that his own parents are lying to him, and must unravel the truth with the help of his only friend, an enigmatic girl named Haley (Sadie Sink) who lives nearby.
Contains examples of the following tropes:
- Alone with the Psycho: Eli begins to feel that he's alone in a facility full of them.
- And Then John Was a Zombie: Perry, Dr. Horn's previous patient, also claimed that he was seeing ghosts. He would eventually become one of them.
- Apocalyptic Log: The medical files Eli finds show each patient's deterioration. For Treatment 1, they look healthy. The Treatment 2 page shows the child looking weak and sunken-eyed. The Treatment 3 page shows them dead on the operating table.
- Arbitrary Skepticism: All the adults in the facility are there to deal with the son of the literal Devil, yet for some reasons none of them believe Eli when he talks about seeing ghosts.
- Arc Words: "Lie."
- Awful Truth: Eli isn't sick at all. He was fathered by the Devil, and his allergic reactions are a side effect of his manifesting powers, which he hasn't learned to control yet. Also, the medical facility is actually an extermination center for children like him. Each child before him was subjected to painful experiments and then killed when this failed to suppress their powers. Eli's human father was also well aware this was going on, and ultimately tries to kill him.
- Bait the Dog: Eli's father appears to be trying to reconcile with him toward the end, but it's a ruse so he can try to sedate him. Later, he looks like he's going to stop the doctors from harming Eli, but then gives Dr. Horn the knife and gives her the go-ahead to kill him.
- Beware the Nice Ones: Eli's a sweet kid, but picking on a child with demonic powers one time too many tends to backfire, especially when he's aware that you've murdered most of his siblings.
- Big Brother Instinct: The ghosts are Eli's half-siblings, who are trying to protect him from Dr. Horn.
- Bitch in Sheep's Clothing: Dr. Horn seems very warm and maternal while doing horrible things to her patients, and telling them it's for their own good.
- Blatant Lies: Rose overhears Paul and Dr. Horn ominously discussing how Eli's treatment isn't working, and they'll "just have to do it." When her husband sees her, he claims they were talking about Eli's escape attempt the previous night. She doesn't buy it.
- Bullying a Dragon: The film runs on this. Every child with undeveloped demonic abilities is subject to unethical experiments and then killed when this fails to contain their powers. Eli is stronger than the rest of them, and shows why this really isn't a good idea.
- Contrived Coincidence: The password that allows Eli to access the medical records just happens to be "LIE" written upside-down.
- Cool Big Sis: Haley is Eli's half-sister, and has special powers of her own, while doing her best to save him from the fate of their other siblings. Agnes Thorne also counts, as she tries to do the same from beyond the grave.
- Cruel and Unusual Death: What "Treatment 3" does. The other kids who died have a greenish hue, Blood from the Mouth, and one of them looks like half his face melted. There seem to be different variations of it, as one of the kids took four days to die from it.
- Dark Is Not Evil:
- Eli seems like a normal kid with undeveloped powers that he didn't even know he had. He shows no desire to hurt anyone who isn't trying to torture and kill him. You just shouldn't push him too far.
- The ghosts aren't trying to hurt Eli, but to warn him about what will happen if he stays at the treatment center.
- The Dead Have Names: When Eli finds the medical files on the other children who were killed, he reads each child's name aloud.
- Deadly Euphemism: Dr. Horn and Eli's father are shown discussing how he isn't responding to the treatment, and that they'll "just have to do it."
- Deal with the Devil: Satan regularly offers to allow infertile women to have children, at the cost that the child will develop special powers.
- Devil, but No God: Satan is very much real, and apparently has a history of making deals with infertile women to allow them to have children who will carry supernatural powers. There's no sign of God doing anything about this.
- The Dog Bites Back: Dr. Horn and her associates spend the movie torturing Eli simply for having undeveloped powers that he doesn't understand, and have been murdering every other child they treated after the initial experiments were deemed a failure. They try to do the same to Eli, who tears them apart with his newfound powers.
- Everyone Has Standards: The breaking point between Eli's parents is that Paul is willing to kill him if the therapy doesn't work, while Rose is not.
- Exact Words: Dr. Horn certainly believes that she's "saved" all of the patients that she's treated. It's their souls she's interested in.
- Five-Second Foreshadowing: When Eli looks through Perry's file, the look of horrified pity on his face when he sees the page for Treatment 3 hints at what we're about to see, that the treatment killed him.
- Foreshadowing:
- When Eli's mother says she has faith that he can be cured, her husband comments, "I've always been a very faithful man."
- Dr. Horn comments that isolation is good for the soul, comments on the "purity" of the facility's water, and doesn't give a straight answer on how many patients she's cured.
- The medical facility has a lot of symbols that resemble an upside-down cross.
- When Eli is being weighed, a nurse says in Spanish, "Seis, sesenta y seis." In context, she just made a mistake about his weight before stating the correct number (66 pounds) but when you put those numbers together, you get 666.
- Another nurse asks Eli "Do you know what happened to the boy who asked too many questions?", after he been asking a lot of questions. When Eli said "he got answers?", the nurse subtly shook her head.
- Freeze-Frame Bonus: If you pause when Eli is reading Dr. Horn's files, there's a lot of information about him and the other children. It's noted that Eli has suffered depression in the past and likes biking, while Agnes Thorne, his half-sister is said to like sweets and to not like school.
- The Fundamentalist: Dr. Horn and her staff are a group of nuns who believe they're fighting Satan by killing all of the children that he fathered, regardless of whether the children showed any sign of being evil.
- Genre Blind: After hearing Eli talk about the ghosts he is meeting, Dr. Horn and her staff do nothing to look into it or to try and ascertain their goal, which turns out to be their undoing when they end up helping Eli. No one also seems to consider that the son of Satan might resort to tricks and deceit to escape.
- Ghostly Goals: The ghosts are Eli's half-siblings, who were killed by Dr. Horn, and are trying to warn Eli of her real intentions.
- He Knows Too Much: When Eli reveals that he knows about the other patients who died, Dr. Horn uses his "delusions" to claim that the therapy didn't work, and that the third, fatal treatment is necessary.
- Hypocrite: Eli's mother claims that "the Devil always lies" when she herself has been lying to Eli for all of his life.
- Ironic Name: The person who thinks she's vanquishing the Devil is named Dr. Horn.
- Keeping Secrets Sucks: Eli's parents are both lying about what's wrong with him, and his father is keeping his wife in the dark about the fatal nature of the treatment.
- Kill It with Fire: Eli's "treatments" consist of injecting him with holy water, which, given his nature, he finds agonizing, as it burns his insides. Eli then turns this back around on the medical staff at the climax, setting them on fire and burning down the facility.
- Knight Templar: Dr. Horn feels that the children she's treating are evil for existing and must be "cured" of their abilities, and killed if that's not an option.
- LEGO Genetics: Apparently, injecting holy water into the system is supposed to turn a half-demon into a full human.
- Locked Out of the Loop: Paul is well aware that the treatment could be fatal, and is keeping his wife in the dark about it.
- Maybe Magic, Maybe Mundane: When Haley shows Eli that she can light fires with her mind, Eli thinks it's a trick. He's later shown reading a book that shows how to do the trick, and says, "I knew it." Haley actually does have powers, as she's another one of Satan's children.
- The Mentally Disturbed: Agnes Thorne's file says that she was referred for "irrational behavior" and engaged in self-harm. In the checklist of mental health symptoms, she has many more boxes checked than Eli.
- Offing the Offspring: Eli's father considers this an option if the initial treatment fails, and ultimately tries to do it himself.
- Only Friend: Haley is this to Eli, being the only one to believe him and encouraging him to fight back. She turns out to be his half-sister.
- Parental Betrayal: Eli's parents aren't telling the truth about what's wrong with him and what the treatment is for. Eli's father is also keeping his wife in the dark about the fact that the treatment isn't guaranteed to work. That turns out to be a massive understatement.
- Playing with Syringes: It's revealed that the medical facility performs painful experiments on children.
- Rule of Three: Each patient goes through three treatments. The third is always fatal.
- Rewatch Bonus: On a second viewing, you can identify which of the ghosts Eli is seeing. He meets Agnes first, Perry second, and Lucius last.
- Satan Is Good: Seemingly in play, but ultimately subverted. Satan does allow infertile women to have children, and his children are normal and don't appear to be inherently evil. However, he waits for the woman to be desperate and lies to her about the outcome. He then abandons his children and waits for them to find him, but only after they "prove" themselves, which they must do by unleashing their abilities, and is perfectly fine to watch those who fail die in the process, also forbidding their other siblings to help them or reveal the truth. The children don't seem to be naturally evil, but he rigs the game by putting them through an ordeal that has them either die or become so.
- Self-Harm: Agnes's medical file notes that she was cutting herself.
- Shout-Out:
- When arriving at the treatment center, Eli's mother tells him, "This is a clean house."
- One of Eli's half-siblings is named Agnes Thorne.
- One of Eli's injections contains tannis root.
- Teens Are Monsters: The group of teenagers who make fun of Eli when he's in his hazmat suit.
- Walking Spoiler: The reveal of what Eli's treatment is really for is a major twist.
- Wham Line: When Eli finally confronts his mother in the climax, it's here that the truth is all laid bare.Eli: (as he painfully levitates Dr. Horn and the nurses around the room) What has she putting been putting inside me?
Rose: Let them go…
Eli: (points at her) What have you been putting inside me?!
Rose: M-Medicine. It’s to make you feel better.
Eli: LIE!
Rose: Holy water! It was holy water. Injections with tannis roots, suppression medication while she worked on your genes.
Eli: …What am I? WHAT AM I?!
Rose: You're our son.
Eli: LIE!!! (sets Dr. Horn and the nurses on fire)
Rose: You're MY son!
Eli: …And my father?
Rose: I prayed, Eli! I prayed every day!
Eli: Prayed to who?
Rose: (Beat as she can't barely bring herself to look at him)
Eli: …PRAYED TO WHO?! (lets out a burst of power that knocks everyone back) Prayed. To. Who?
Rose: The Lord didn't answer me… but your father did. He promised me you wouldn't be like him, Eli… but he lied. The Devil always lies. - Where's the Fun in That?: Haley knows what's going on, but insists that Eli has to figure it out on his own. It turns out Satan actually forbids his children from helping each other, possibly to ensure they go through an ordeal that will make them snap.
- Would Hurt a Child: Dr. Horn and her associates have been killing all the children at their facility in the third stage of treatment, after the initial treatment was deemed a failure.
- Your Head A-Splode: When Eli's father tries to stab him, Eli responds with this. Although it's technically inverted, since it's an implosion.
