Cerebro is calling out an intruder alert prompting the X-Men to dawn their uniforms and come to the Professor's study to learn who this mysterious intruder is. Telling his charges that whoever is approaching the mansion is extremely powerful, he sends the group out to set up defenses including an ice wall, live-wire lined trench and fence posts rigged with grenades. When the X-Men return to the Professor, they are shocked to learn that their attacker is none other than Xavier's own brother.
The Professor tells his X-Men that his father was a nuclear research scientist who was accidentally killed during a nuclear bomb test in the New Mexico desert. During his father's funeral, Kurt Marko -- his father's assistant -- would come to comfort Xavier's mother. However, the young Charles, already developing mental abilities, could read Kurt's mind and learn of his less than noble intentions to take his mother and his father's wealth, two things that Marko had become envying of.
Shortly thereafter, Kurt would move into the Xavier mansion, and marry Charles’s mother. Kurt became a ruthless and verbally abusive step-parent and would shun his new family for his work. During this time Kurt's true motives would come out. One day, Kurt would be thrown into a fury when his own son from a previous marriage, Cain, came to the Xavier Mansion after yet another expulsion from school. Cain turned out to be a cruel tormentor to young Charles.
The Professor's narrative is interrupted when Cain's advancement on the mansion progresses, easily smashing through the ice wall put up by Iceman, much to the X-Men's surprise. Charles continues the story of his youth: He would explain one day that he would overhear Kurt and Cain arguing over money. When Cain suggested that Kurt had orchestrated the death of Charles's father (an accusation that Kurt would flatly deny) Charles entered and confronted Kurt. During the moment of tension, Cain tried to throw chemicals at Charles; however Kurt attempted to stop them sending the volatile brew crashing to the floor, causing an explosion and fire. Kurt carried the two boys out of the blast. Having been mortally wounded in the blast, he begged Charles to believe that his father's death was only an accident before dying.
As Cain manages to break past the trench and live-wire trap on the mansion grounds, Charles plays for time to finish the final part of his story. He explains that by his adulthood he found that his mental powers (which by this point have rendered him bald) could allow him to have an advantage over other students, however he decides against it. Xavier then decided to challenge his body, as his mind was already vastly superior, and got into sports.
His trophy winnings earned the ire of Cain who pushed Charles too far one day and the two got into a fight which Charles won due to his superior fighting skill. Some days later, Cain attempted to make Charles cry out in fear by driving recklessly. He only succeeded in making the car drive out of control and smash through a detour sign and down a cliff. Cain bailed out, but Charles wasn't so lucky, however Charles would tell his X-Men that he was able to erect a mental shield around himself to protect him from the crash.
Outside the mansion, Cain finishes with the live wire and still manages to get past the grenades and gas traps that were set out for him. With their attacker mere feet away, Iceman puts an ice barrier over the window of Xavier's study to allow the Professor to tell the final part of his story: How the now adult Cain and Charles were enlisted in the military and would be sent to fight in the Korean War. The two were separated from their unit and were forced to seek refuge in a cave to escape enemy fire. Inside the cavern, Charles and Cain discovered the long lost temple of Cyttorak. The greedy Cain grabbed a crimson gem that was left before an altar. Upon contact, the gem absorbed itself