The X-Men are training in a Danger Room simulation. Their objective was to rescue Storm from the enemy. The mission is going smoothly and Cyclops and Nightcrawler have teleported into the building holding their hostage. Suddenly, Jean who is holding both guys telekinetically up in the air from the roof of the building, is jumped from behind, and she loses her concentration and her grip. Cyclops and Nightcrawler fall to the ground. When they get to the hostage, Cyclops realises that she is not Storm, but Rogue. Rogue attacks Cyclops, and he ends the simulation abruptly, upset that Professor Xavier had thrown in “an element of surprise” that he wasn’t expecting. Xavier advises him to always expect the unexpected in real life.
Scott and Jean set off for school to prepare for their field trip. Scott confides his troubled mind in Jean, the fact that Xavier used Rogue in the simulation while ironically, they are trying to befriend Rogue. Principal Darkhomle overhears Scott and Jean’s conversation on that eventful morning, and decides to use that to her advantage, to deepen the rift between Rogue and the X-Men. She finds Rogue in the gym spying on Scott and Jean acting way too friendly with each other. Darkholme has a plan to replace Jean with Rogue on the field trip roster. This surprises both Scott and Jean.
Magneto pays a visit to Xavier, mocking his fear of telling his students the truth about Principal Darkholme.
Back on the bus on the way to the site of the field trip, it begins to snow heavily. The bus skids on the slippery slope, but Scott manages to use his powers to stop the bus in time from going over a cliff. Rogue was the only one to notice Scott’s doing, and they exchange glances. While the teacher-in-charge plans to head back, Rogue spontaneously suggests that they “take [their] snow mobiles out to the cave and wait out the weather there”. Rogue challenges Scott to a snow mobile race and gains the advantage with her aggression.
Xavier is troubled with the truth. Ororo walks into the library with Jean to inform Xavier of the blizzard in the mountains where the field trip is. Xavier is surprised to see Jean back in the mansion. Jean explains to him that she got replaced with Rogue by Principal Darkholme. Xavier suspects there’s more to this replacement.
While in the cave, Rogue wanders off from the group. Scott follows Rogue to a cliff, where she corners him, demanding the truth about using her as “target practice” in their training sessions. Scott tries to explain that it wasn't as it seemed to be, and that they want her on their side. They are ambushed by Principal Darkholme disguised as Scott’s friend, Paul, and she reveals herself to be Mystique to Scott. She catches Scott off guard and pushes him off the cliff.
Rogue is appalled by Mystique’s actions. Wanting to know the truth, Rogue absorbs Mystique, and learns that Mystique has plans to use Rogue for her own actions. Rogue immediately goes to the aid of Scott, but Mystique forces them into the river below the cliff. Rogue and an injured Scott find themselves cornered on a bridge of rock by Mystique. Scott senses the X-Men are near, but he’s too weak to make contact. Rogue takes Scott’s glasses off, releasing his optic blasts into the air to signal to the X-Men. Rogue also absorbs Scott’s powers to blast the approaching Mystique. Wolverine arrives in the X-jet and drives Mystique away, rescuing both Rogue and Scott.
Back in the mansion, Xavier comes clean on the truth about Principal Darkholme being Mystique in disguise. The Institute’s students also welcome Rogue into their family.