The Beast again faces the perils of the Danger Room. He is eventually tripped up by a grabbing a false rope to try to swing over a water hazard. Iceman is next through the gauntlet but is too cocky at his young age and is quickly defeated. Angel humiliates him by hanging him from a wall hook. Once Iceman is rescued by Marvel Girl it is time for her test. She opens a box for Professor X which hides a cake. It has been one year since the X-men were first formed.
Meanwhile at another table, four other mutants bicker with each other. They are the Toad, Mastermind, Scarlet Witch and her brother Quicksilver. Scarlet Witch becomes insulted by one of Mastermind's propositions and uses her hex power to dump a pitcher of water in his lap. Outraged, Mastermind makes a move to harm Scarlet Witch but she calls her speedster brother Quicksilver to save her. The toad reminds them that the leader, Magneto, would be upset by them fighting and they stop. Magneto is away from their island lair stealing an old ex-convoy freighter.
Angel spots the freighter that seems unmanned and reports it to Professor X. The Professor is concerned but is unsure how to proceed. Magneto returns home to find that his brotherhood has been infighting and he is not pleased. We also hear that Scarlet Witch is working for Magneto out of obligation to him because he saved her from a bunch of angry villagers.
Later, Magneto begins a plan to take over the island nation of Santo Marco. The X-men are alerted to this by a newspaper report of a mysterious unmanned vessel shelling the country. Professor X reaches out to Magneto on the astral plane to try to come to an understanding. Magneto makes it clear that because Professor X vows to protect humanity, it has made them mortal enemies.
The Brotherhood of Evil Mutants successfully takes over the island of Santo Marco using Mastermind's illusionary army. Once in power Magneto estabilishes a legitimate army that appears the same. He rules with an iron fist while preparing for the coming of the X-men. When the X-men arrive Professor X details the plan for them to attack Magneto's castle from multiple points to catch his team off-guard. The Beast scales the castle walls, disables two guards only to be knocked back over by the Toad. While clinging to the wall, Mastermind projects an illusion that the wall has become as smooth as glass and Beast falls out of sight. Angel is able to fly inside but is harassed by a green clothed speedster, although he can't out run Quicksilver he can out maneuver him. Angel is able to dodge and Quicksilver slams into a wall knocking himself unconscious. The Scarlet Witch sees her brother in peril and collapses a wall on Angel.
Magneto and his soldiers arrive to bind the Angel only to be assaulted by Cyclops. Quicksilver recovers and puts Cyclops in a headlock, this prevents him from lowering his visor which blasts through the ceiling and causes Magneto's generator to go critical. The Brotherhood retreat to another part of the castle, as Cyclops is able to use his optic blast to push the generator out of the castle.
Angel, Iceman, Cyclops, Marvel Girl and Beast reunite but get trapped by a wave of boiling oil. Professor X senses their panic and arrives to rescue them. The boiling oil is only one of Mastermind's illusion. Before the Brotherhood of Evil Mutants leaves, Magneto sets an explosive trap for the X-men and nuclear bomb to destory the island. Quicksilver and Magneto are shocked that Magneto would murder all the people of Santo Marco. Quicksilver darts back and disarms the nuke.
Professor X is injured by the detonation of the other bomb. A injury so severe it robs him of his telepathy.
This is the first appearance of The Brotherhood of the Evil Mutants, and also of Toad, Mastermind, Scarlet Witch and Quicksilver.