Cerebro picks up the signature of an unidentified mutant. Beast, Angel and Iceman head off to investigate. They track the mutant, Sunfire, to “the Central Plaza of the United Nations”. Sunfire has gone to the ceremony of Mr Yoshida’s unveiling of a marble monument to “the youth of the world”. Sunfire proclaims Mr Yoshida a “traitor” and destroys the monument. The X-Men arrive to stop Sunfire, but are outmatched by Sunfire.
Angel and Iceman take the injured Beast back to the Institute. Scott and Jean had been out shopping during the incident. Jean examines Beast’s injury and finds it to be a bad sunburn. She confines him to bedrest while the rest of the X-Men track down Sunfire.
Sunfire is working with his uncle. His mother survived the Hiroshima bombing but a few years later died giving birth to Sunfire. His uncle, Tomo, helped raise Sunfire, and trained him in using his mutant powers when he manifested. Tomo groomed Sunfire to take revenge on the United States for their atomic bombings on Japan.
Using Cerebro, the X-Men track the mutant to the U.N. and in a “diplomatic vehicle”, which they cannot interfer with. Cyclops tells Angel to pull back his pace and just follow the vehicle while Marvel Girl keeps in “mental contact”. The X-Men track the mutant, with the Japanese delegate and his team, to the airport.
Angel takes to the skies to follow the airplane. He gets too close and is almost sucked into an engine but Marvel Girl is able to telekinetically pull him away. The airplane arrives at Washington D.C. Sunfire’s father, delegate Saburo Yoshida, overhears Sunfire conspiring and slaps him, angering Sunfire.
Meanwhile, Soctt and Jean are not able to get into the Capitol to investigate. They can only wait for Sunfire to reveal himself.
Later, Saburo walks in on his son changing into his Sunfire costume. Tomo distracts Saburo while Sunfire takes off to accomplish his mission. Angel tackles Sunfire in the air. Iceman barely throws up ice shields in time to protect Angel and himself form being burned. Cyclops and Marvel Girl are left standing to take down Sunfire. The panicked public are on a rampage to leave the Capitol.
Cyclops has Marvel Girl levitate him to the dome of the Capitol. Sunfire directs a blast at the Capitol’s dome, but that is countered by Cyclops’ optic blast. Sunfire forces Cyclops off the dome. Marvel Girl intervenes, breaking up the fight in midair. Cyclops is safely lowered to the ground. Saburo climbs to the dome and tries to talk sense into his sun. Tomo pulls out a gun and murders Saburo, his brother.
Sunfire realises too late that his hatred instilled by his uncle has led to his father’s demise. Yet with his dying breath, Saburo encourages his son to “live only...for the future” and not focus on the past and seeking revenge. The X-Men watch from a distance Sunfire grieving for his father.