NOTE: This spoiler was submitted by Jeremy

The film starts with Dani Moonstar (Blu Hunt) mentioning how her father used to tell her that inside everyone were two bears – the good one made up of compassion and kindness, and the evil one made up of fears and aggression. Cut to Dani waking up as her father William (Adam Beach) waking her up, as their reservation appears to be hit by a tornado. As the residents flee, William hides Dani behind a tree as he goes to help the others. Moments later, William is thrown back in front of Dani, dead. She tries to run for it as a a growling entity approaches her, but she tumbles down a hill.

Dani wakes up in a facility. She meets Dr. Cecilia Reyes (Alice Braga), who tells her that she is in a kind of hospital for people with abilities like hers, and that she is the sole survivor of the incident on the reservation. Reyes tells Dani that she is a mutant, but Dani is not aware of any powers she may has.

Reyes holds a session with the other members of the facility – Rahne Sinclair (Maisie Williams), who has the power to turn into a wolf and suffered trauma from when the priest of her church tried to kill her; Illyana Rasputin (Anya Taylor-Joy), who carries a purple dragon hand puppet that she calls Lockheed; Roberto da Costa (Henry Zaga), who comes from a wealthy family from Brazil; and Sam Guthrie (Charlie Heaton), who appears with a black eye and broken arm. As Reyes tries to counsel the teens, Dani joins them. She is greeted with smarmy remarks from Roberto and Illyana. Reyes has Ilyana show Dani around the campus, but Illyana couldn’t care less and just sprays graffiti on a nearby fountain. When Dani tries to run away, she ends up running into a forcefield. Illyana laughs at her, but when Dani tries to attack her, Illyana just disappears in a flash.

Dani contemplates jumping from the clock tower, but Rahne comes up to talk her out of it and convince her to stick around. After helping her back in, Rahne shows Dani around the facility a little more. She shows Dani that Sam’s superpower is flying at super speed, which he practices by hooking himself up to a large weight, and it causes him to hurt himself since he doesn’t know how to fully control it. Roberto won’t say what his power is, and the girls agree that Illyana is the worst.

Dani returns to her room to sleep, while Reyes monitors her and the other teens. Dani dreams about the incident at her reservation, and Reyes notices readings of psionic energy coming from Dani.

Sam and Roberto are in the laundry room until Roberto leaves. Sam hears a banging coming from one of the washing machines. He approaches it and sees a hand pressed against it. It takes him to a mine he used to work in back in Kentucky. He walks past other miners until he reaches his father (Thomas Kee), who appears undead. Sam is then blasted against the wall by the force in the machine.

Later, the teens are in the recreation room, when Illyana makes more derogatory comments to Dani (“Pocahontas”, “Standing Rock”). Dani doesn’t take the abuse any longer and calls out Illyana’s behavior, which leads to them fighting. After Dani punches her, Illyana’s right arm produces the Soulsword, which she almost uses against Dani until Reyes comes in and uses her forcefield to stop the fight, then put the girls in solitary confinement. Dani overhears Illyana whispering to herself in her room. She is shown having a flashback to her childhood where a tall, gaunt man in a smiley mask loomed over her. Dani later has a nightmare where she finds herself in the snowy woods close to where she lost her home and father, and a monstrous entity tries to attack her. Reyes finds her covered in something wet, and she proceeds to take more tests from Dani.

Rahne goes to the chapel for confession. She hears what sounds like a voice telling her she is inhuman and will go to Hell. Rahne runs out of the chapel to avoid what she thinks is a demon.

After Reyes falls asleep, Sam and Roberto invite Dani and Rahne to join them (and Illyana) up in the attic since it’s the one place that is apparently not monitored. They mention Reyes’s superior that she keeps alluding to, stating that after their time there, they may go to the facility for special mutants. The guys think she is talking about Professor Xavier and his Mutant Academy. Illyana then has them do lie detector tests, wherein it is revealed that she killed 18 men in her old town. She asks Dani about her bear necklace, which was given to her by her father.

It turns out Reyes was monitoring the attic as well and tries to admonish the teens for disobeying her. Later, Illyana spikes her tea to get her to pass out, and the teens proceed to have fun. Dani and Rahne dance together, Illyana makes fun of Reyes, and Sam and Roberto spend time together. Sam tells Roberto that he accidentally killed his father and half the miners when he lost control of his powers. Roberto refuses to say what happened that got him into the facility. Dani and Rahne go outside where Rahne shows Dani the night sky under the forcefield, which looks lovely. The two then share their first kiss. Meanwhile, Roberto finds Illyana in the pool. They start to hook up, but he reveals that he burned his girlfriend to death with his powers. Illyana says he cannot hurt her, but moments later, she appears to vanish. A demonic creature appearing as Roberto’s girlfriend on fire then tries to attack him. He rages out and his fire powers are activated. The others come in to help him, and Reyes pushes him into the pool. Illyana appears and says she was never in the pool.

Reyes punishes Illyana for drugging her by confining her to her room. Rahne takes a shower and sees the demonic image of her priest (Happy Anderson), whom she killed, approaching her with a W branding iron similar to one he used on her back years earlier. The priest brands Rahne’s neck, and the others try to calm her down. Illyana somehow gets out of her room and tells the others that all of this is happening because of Dani. She tries to attack her again with the Soulsword and transports her briefly to a hellish landscape before Dani snaps her out by manifesting one of the creepy smiley masks to scare Illyana. Reyes runs more tests on Dani, and Dani starts seeing visions of mutant children being tortured at the Transigen facility (from “Logan”), making her realize that they are not going to be sent to the Mutant Academy. Reyes reports to her real employers, the Essex Corporation, who determine that Dani’s power makes her a threat, and that she must be killed.

Dani goes to Illyana’s room to try and talk to her. She gives her back Lockheed since she dropped him, and Dani asks her where she transported her to. Illyana says it’s Limbo. She explains that her powers manifested when she was kept as a prisoner by the men in masks (Smiley Men).

Reyes takes Dani away for what is supposedly one last test. Rahne follows as she knows something is not right. Reyes tries to put Dani to sleep before injecting her IV with poison. Rahne uses her wolf powers to sneak through the vents and attack Reyes, clawing at her until she flees, and Rahne saves Dani. Meanwhile, Illyana and Roberto are attacked by the Smiley Men, who remove their masks to reveal their hideous blind faces. After using the Soulsword and Sam’s speed to kill the Smiley Men, the teens go into Reyes’s office to find files on them. Illyana was the most viable candidate for Essex since she is classified as a killer, but they learn that Dani’s power was going to have her killed. They figure that, in order to leave the facility, they have to find Reyes and kill her.

Rahne sniffs out Reyes’s trail, but she traps the teens in her own forcefields. She tells them that Dani’s power is to bring out your greatest fears and traumas to use against you. Before she can kill Dani, the facility comes under attack by the Demon Bear, the entity that destroyed Dani’s home. The Demon Bear mauls Reyes to death, which breaks the forcefields, but the Demon Bear proceeds to attack the teens. Illyana goes into Limbo with the Soulsword and brings Lockheed to life to fight the monster. They take the fight to the chapel, where Dani is unconscious as she feels she is not strong enough to fight it. Sam and Roberto unleash their own powers to fight back, while Rahne wolfs out to claw at the creature’s face. As the others are getting demolished even with their powers, Dani sees a vision of her father encouraging her to fight back. Just before the Demon Bear can devour Rahne, Dani wakes up and talks to it calmly, bringing it to a non-monstrous form that goes to rest and no longer harm them.

The sun rises on the new day. The teens discover that the forcefield barrier has gone down, meaning they are free. Dani thanks the others for saving her, but Rahne says she saved them. They all then decide to head into the nearest town as they start new lives.

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Five mutant teens - Dani, Illyana, Rahne, Roberto, and Sam - are kept in a testing facility under the watch of Dr. Cecilia Reyes. Each of them suffered a past trauma connected to their powers.

Dani's reservation was destroyed and her father was killed by what was believed to be a tornado but was really an entity of fear called the Demon Bear. Illyana was a prisoner of a group of kidnappers with smiley masks, and she has the ability to manifest the Soulsword and travel to Limbo to fight her enemies. Rahne can turn into a wolf and was branded by a priest in her old town. Roberto can produce fire energy and accidentally killed his girlfriend that way. Sam can fly at super speed but accidentally killed his father when he realized his power. All of these fears become real when Dani arrives, as her power is to use one's fear against them in such a way.

Reyes tells the teens that she is prepping them to join what they think is Xavier's Mutant Academy, but in reality, is the torture facility Transigen from the Essex Corporation. After she is instructed to kill Dani, Rahne saves her by attacking Reyes. After the teens fight entities resembling the Smiley Men, Reyes tries to capture the teens but is killed by the Demon Bear. Dani is knocked unconscious while the other four use their powers to fight the Demon Bear. Dani sees a vision of her father encouraging her to overcome her fear, which she does and uses this to calm the Demon Bear down into a less monstrous entity that finally rests.

With Reyes's barrier gone, the five teens head to the nearest town together as new friends who are now free.