- The X-Men
- Brotherhood of Evil Mutants (First appearance)
- Apocalypse (En Sabah Nur) (First appearance)
- Gisela (First and only known appearance)
- Airline passengers
- Muir Island mutants
- Cody Robbins (First appearance) (Only in flashback)
Races and Species:
- Earth-92131 (Main story and flashback)
- Earth (Main story and flashback)
- United States of America (Main story and flashback)
- United Kingdom
- Earth (Main story and flashback)
- X-Men Blackbird
- Rogue's Car
A doctor at the Muir Island Mutant Research Center claims to have found a cure for the mutant gene. Rogue travels to the island, seeking the "cure". She visits Dr. Adler and tells him how she is considering the treatment. Dr. Adler sends her on her way and Apocalypse appears. "Dr. Adler" reverts to Mystique and they discuss Rogue's powers. Later, Cable attacks Dr. Adler, but the X-Men defeat them. Rogue changes her mind about the treatment and leaves. At the end, Warren (Angel) comes for the treatment and goes into Dr. Adler's lab. Mystique finds Apocalypse and tells him of Warren, and he replies that he is planning on destroying the world.
Gisela and Warren Worthington sit in a cabin, and Gisela says she should be afraid because he keeps a "mad scientist" in the cabin. Warren says the man's name is Gottfried Adler, who is actually now in Scotland to do research. Cable sneaks up on Warren and asks for Adler. Cable shoots at Warren, who falls off the balcony and into the snow. Cable asks Gisela about Adler, and finds out that the scientist is on Muir Island. Angel flies in with his mutant wings, but Cable escapes. Gisela accidentally fires at Warren.
At the Muir Island Research Center, Professor Xavier asks Moira MacTaggert to review Dr. Adler's work, but Moira says she can not. As Dr. Adler turns down the professor's offer to visit, Xavier tries to probe the doctor's mind, instead seeing visions of two mutants. The professor wonders if Dr. Adler could be a mutant and decides to tell his X-Men about the doctor's work to "cure" mutantkind.
The X-Men continue their work (from the previous episode) of rebuilding the X-Mansion. Wolverine orders around his fellow mutants, blaming the mess on Gambit. Wolverine and Gambit confront each other, but Rogue breaks up the fight. They speak with Professor Xavier, who tells them about Dr. Adler's treatment. Xavier says there is no right or wrong about whether or not a mutant chooses to keep their mutation.
Rogue drives away from the mansion, but Gambit follows her. Rogue flies up and hitches a ride on a passenger plane's wing. She jumps off when she finds Muir Island. Avalanche and Pyro wait for the shape-shifter Mystique in a Muir Island pub. They suspect Rogue might be her, but she throws them at the wall. Rogue visits Dr. Adler and asks him if she can try out his cure. Dr. Adler says he will consider her offer. When Rogue leaves, it is revealed that "Dr. Adler" is actually Mystique. Apocalypse tells Mystique to make her his slave instead of taking away her mutant powers.
Rogue thinks about her decision, remembering when she first kissed her boyfriend Cody Robbins, taking away his power. While Pyro searches the shores for Avalanche, he runs into Cable, who is still looking for Dr. Adler. Cable shoots him, and Avalanche recovers Pyro from the water. Pyro decides that since there is such a "high demand" for Dr. Adler, he and Avalanche should kidnap him.
Rogue agrees to go through with Dr. Adler's "treatment," but Avalanche and Pyro arrive on the scene and kidnap the "doctor" before he can finish. Rogue and Cable pursue the two villains. Pyro and Avalanche discover that they are actually kidnapping their team member Mystique. Meanwhile, Xavier investigates the kidnapping scene and Cyclops and Jean join him, saying they suspect Rogue came here to undergo Dr. Adler's treatment. Rogue fights off Pyro and Avalanche while Cable deals with "Dr. Adler." Cable threatens to push Dr. Adler off the cliff because of his involvement with the Genoshan Mutant Collar program. Rogue tries to save Dr. Adler, but Cable stops her with a plasma grenade. Mystique reveals her status as a shapeshifter to stop him from killing her. The X-Jet introduces Xavier, Cyclops, and Jean into the fight. Cable falls over the side of the cliff, but grabs a hold of the rocks on the side. Jean also falls off the cliff, but Rogue saves her from the rocky shores.
Rogue helps Dr. Adler repair his equipment, but this time declines his offer to be cured. She bumps into Angel on her way out, who asks Dr. Adler for treatment. Mystique tells Apocalypse that she has found him another mutant slave. Apocalypse says he must destroy the world.
- The mutants Professor Xavier sees when he tries to read Mystique (shapeshifted into Gottfried Alder) are herself and Apocalypse.
- Although Doctor Adler died some time prior to the episode, Mystique reveals that he was indeed real until Apocalypse killed him. Cable reveals that it was Adler who created the mutant suppression collars used on Genosha (as seen in "Slave Island").
- The use of the last name Gottfried Adler is likely used on purpose given the fact that Mystique poses as him in this episode. It is likely a shout-out to Earth-616 continuity, as in that reality Mystique's confidant and one-time lover Irene Adler (aka Destiny) has the same name.
- Rogue's origins detailing her kiss with Cody Robbins is adapted from Uncanny X-Men #185.