The X-Men have been captured by Count Nefaria, who had hoped to take in the young Mutants as his allies, only to learn that they are truly heroes. Nefaria tells the X-Men he will give them an hour to change their minds. Despite this setback, Nefaria still launches his current plan: To steal the entire city of Washington D.C. Nefaria accomplishes this with a special device that traps the capital city under a clear and indestructible dome. The dome’s appearance spreads panic all over the city, causing government officials call in the military from the Pentagon. However, no matter how hard they try and what they use, nothing can pierce the dome.
Nefaria then sends out his impersonation X-Men to the Capital Building to present his ransom: One million dollars, to be paid immediately. When the government refuses and guards attempt to capture the faux-X-Men, they are shocked when they suddenly vanish. They still believe that they were the genuine article for they don't know the exact extent of their Mutant powers.

Inside Nefaria's base, the real X-Men attempt to break free with the use of Jean’s mental powers, breaking them free of their shackles. As this is happening, the Professor gets a call from General Fredricks about what is happening and he agrees to travel to Washington at once. When attempting to contact his students, he finds that they are out of his reach. Back at Nefaria's base, Jean manages to remove the shield that has been put over Cyclops' visor, and Cyke uses his optic blasts to save the others. The Professor manages to get through to the X-Men and manages to give them instructions.
Nefaria meanwhile has been contacted by the government who agree to his terms, much to his delight. Impressing him further is the arrival of the X-Men who agree to join forces with him. Warning the group against a double-cross, Nefaria tells them of a failsafe on the device: Only he can operate the machine that controls the dome, if anyone else were to attempt it, it would cause the dome to explode, destroying Washington D.C. As Nefaria sends the X-Men go to collect his ransom, his previous minions, Porcupine, Plantman, Unicorn, Eel and the Scarecrow, all agree to turn against Nefaria to seize the million dollars for themselves.

The Professor arrives at the military attach? outside the dome where General Fredrick's tells the Professor of the X-Men's "involvement" in the ransom, and the Professor asks for some time to think things over. In reality, he sends his astral form into the dome to spy on Nefaria and learn his secrets. The X-Men travel outside the dome and are provided with an opening so that they can collect the ransom from the military. They head toward the meeting spot unaware that Nefaria's betraying minions are watching and waiting to strike.
The X-Men collect the money, but are sent fleeing when a trigger happy soldier attempts to shoot at them. They also attract the attention of an angry mob that chases after them, throwing bricks. However, the crowd is scared off by Porcupine and the other crooks that then confront the X-Men and demand that they hand over the money. As the X-Men and the super-criminals fight over the loot, the X-Men defeat all them all except for the Eel and Unicorn, who rush toward the case filled with money. The Unicorn then betrays his comrade by blasting him and running off with the money. Unicorn doesn't make it very far when he's surrounded by both the X-Men and the military. However, he manages to keep them at bay with the power of his unicorn blaster.
The X-Men keep the military at bay while they take back the money from Unicorn. Cyclops hands it over to Marvel Girl and sends her back to the truck that is waiting for them. Spotting the girl with the money, the regrouped villains try to give chase but are held back by a group of soldiers. Despite the fact that Plantman manages to wrap them up in vines, they are too late to stop the van from driving off with only Marvel Girl

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