Plot
Superman saves the crew of a Russian space station before uncovering the capsule that brought him to Earth and retrieving a green Kryptonian energy module. A recording left by his mother Lara reveals the module's power can only be used once. Returning to Metropolis, he discovers that the Daily Planet has been taken over by tabloid tycoon David Warfield, who replaces Perry White with his daughter Lacy Warfield, who develops a crush on Clark Kent.
Meanwhile, Superman seeks guidance in the Fortress of Solitude after learning of escalating tensions between the United States and the Soviet Union over nuclear weapons. He later addresses the United Nations and announces his plan to rid the world of all nuclear arms.
Meanwhile, Lenny Luthor orchestrates a jailbreak to free his uncle, Lex Luthor, from prison. The pair travels to Metropolis, where Lex steals a strand of Superman's hair to create a genetic matrix. Partnering with black market arms dealers, Lex attaches the matrix to a nuclear missile. When Superman intercepts the missile and hurls it into the Sun, the resulting energy discharge creates Nuclear Man, a superhuman entity. Nuclear Man returns to Earth, aligning with Lex, who reveals that Nuclear Man becomes inactive without sunlight.
Superman confronts Luthor after learning what he had done, spurring Luthor to direct Nuclear Man to attack. The two battle across the world until they reach New York City. Superman stops Nuclear Man from throwing the Statue of Liberty into Metropolis, but this distracts him enough for Nuclear Man to slash him across the back with his toxic claws.
Superman develops radiation sickness due to a shock from Nuclear Man and is defeated by being cast away. Nuclear Man returns to Luthor, and they conspire to future victories. Superman is badly hurt by the radiation poisoning, but he retrieves the Kryptonian energy module and uses it to heal himself.
Superman confronts Nuclear Man in a second battle that results in them fighting on the Moon and Superman being driven into the Moon's surface. Nuclear Man, having taken an interest in Lacy, kidnaps her and takes her into outer space. Superman frees himself and creates a solar eclipse by moving the Moon out of orbit, depriving Nuclear Man of sunlight. Superman rescues Lacy and ultimately destroys Nuclear Man by trapping him in the core of a nuclear power plant. This converts Nuclear Man into electrical energy for the power grid.
Back in Metropolis, Perry White secures a loan to regain a controlling interest in the Daily Planet, reducing Warfield to a minority shareholder and ensuring the paper's independence. Superman apprehends the Luthors, placing Lenny in Boys Town and returning Lex to prison. In a closing speech, Superman acknowledges that world peace cannot be achieved overnight but remains committed to guiding humanity toward that goal.
