Danielle "Dani" Moonstar, portrayed by Blu Hunt, is a young Cheyenne Native American who witnesses a devastating storm that wipes out her entire reservation, leaving her as the sole survivor. Hidden in a tree by her father during the chaos, Dani later finds herself in a strangely desolate hospital under the care of Dr. Cecilia Reyes, a strict yet protective mentor and medical professional capable of generating energy fields. Dr. Reyes reveals to Dani that she possesses unique mutant abilities, allowing her to create illusions drawn from the fears and desires of others. She advises Dani to stay in the hospital to learn to control her powers.
Inside the facility, Dani meets four other teens: Samuel "Sam" Guthrie, who can launch himself into the air while invulnerable; Illyana Rasputin, a Russian mutant with sorcery skills; Roberto "Bobby" Da Costa, who can manipulate solar energy; and Rahne Sinclair, a Scottish mutant struggling with her ability to transform into a wolf due to her religious beliefs. Each of these teenagers has faced severe tragedies: Sam tragically caused a coal mine collapse, Roberto accidentally killed his girlfriend during an intimate moment, Rahne killed a priest who branded her as a witch, and Illyana endured childhood trauma from enslavement and abuse.
As Dr. Reyes keeps them under close supervision, the teenagers suspect they are being groomed to join the X-Men, although she warns them that they are considered dangerous and should not leave until mastering their powers. Dani tries to escape but encounters the hospital's force field. While Illyana initially bullies Dani, Rahne is sympathetic, and the two form a bond. Although Dani contemplates suicide, she is stopped by Rahne, fostering a romantic connection between them while Illyana remains antagonistic, even threatening Dani with her Soulsword.
The group begins to experience terrifying visions of their pasts, exacerbated by their fears. Dani reveals that her father used to tell her stories about a "demon bear," which feeds on fear. As the story unfolds, Rahne discovers a way out of the hospital through the ventilation system, leading to a brief moment of intimacy between her and Dani in the garden. However, their peace is shattered when Roberto’s past with his girlfriend manifests during a swim, causing chaos and suspicion among the group.
Dr. Reyes confides that Dani's powers are the source of their nightmares and that she reported their situation to the Essex Corporation, who plans to harvest Dani's DNA and potentially eliminate her. When Dani's powers go out of control during a crisis, the manifestations of their fears escalate into threats, leading to the realization that they need to confront Dr. Reyes to escape. The group learns that her training was not for heroism but for becoming assassins.
In a fierce showdown, Dani unleashes the wrath of the Demon Bear, ultimately confronting her own fears and awakening her strength. Guided by her father's spirit, she calms the beast, allowing the group to escape the now powerless facility and venture into the world to seek their future.
