The full story
Dani Moonstar wakes up in a secure hospital wing with no memory of how she got there, the sole survivor of a tornado that destroyed her Cheyenne reservation and killed her family. Dr. Cecilia Reyes tells her she's a mutant, that this facility exists to help young mutants control their powers before they hurt anyone else, and that graduating means joining the X-Men.
Four other teenagers are already there, each one there because their powers already hurt someone. Sam Guthrie's power to fly at incredible speed collapsed the coal mine he was working in, killing his father and his coworkers. Roberto da Costa's ability to generate and control heat burned his girlfriend to death while they were swimming together. Rahne Sinclair, who can transform into a wolf, fled her devoutly Catholic village after killing the priest who branded her a witch. Illyana Rasputin, who commands interdimensional sorcery and a demonic sword, survived years of childhood abuse and now barely trusts anyone.
As Dani bonds with the others — especially Rahne — visions and manifestations begin overwhelming the facility: a psychic recreation of Sam's mine, Roberto's fire, and eventually a towering Demon Bear that only Dani can see, but that leaves real damage behind it. Reyes insists these are the others' powers acting up, but the truth is Dani's own ability to make fears and memories physically real is the source of all of it — the same power that generated the tornado that destroyed her reservation in the first place.
Reyes secretly reports to the Essex Corporation, whose orders are to extract Dani's DNA and then eliminate her. When Reyes moves to sedate Dani permanently, the Demon Bear — Dani's own fear, finally directed at the person threatening her — breaks loose and kills Reyes. The facility's containment field, powered by Reyes, collapses with her.
With her father's spirit urging her on, Dani faces the Demon Bear directly instead of running, and it dissolves once she stops fearing it. The five teenagers escape the now-unshielded facility together as morning breaks, walking out to find the nearest town rather than the X-Men Reyes promised them.