The film opens in a world fraught with Cold War tensions, where the arms race between the United States and the Soviet Union reaches its zenith. Amid this global anxiety, Superman, who has been the world's beacon of hope and justice, decides to intervene in a manner unlike ever before. Disturbed by the escalating threat of nuclear war, he addresses the United Nations, announcing his intention to rid the Earth of all nuclear weapons in an effort to promote peace. His decision is met with mixed reactions, but Superman remains resolute in his quest and begins to collect and dispose of the weapons, casting them into the sun.

Meanwhile, Superman's nemesis, Lex Luthor, escapes from prison with a scheme to profit from the global fear and to ultimately defeat Superman. He steals a strand of Superman’s hair from a museum exhibit and, using the genetic material, creates a powerful adversary named Nuclear Man. Luthor plans to wield Nuclear Man as a weapon to challenge Superman's mission of peace. With the ability to harness the power of the sun, Nuclear Man becomes a formidable foe, provoking a battle that tests Superman's might and resolve. As the two titans clash, the fate of the world hangs in the balance, with humanity’s hope for a peaceful future resting on Superman’s shoulders.