Plot summary

August "Gus" Gorman (Richard Pryor) is an unemployed loser looking for a job. In the opening scene, Gus is at a Metropolis employment office to seek out more unemployment insurance and he is told that he is no longer eligible for unemployment benefits because of having been unemployed for 28 weeks. As he lights a cigarette with a borrowed book of matches, he sees an ad for a computer-programming school.While taking his classes, Gus discovers that he has a natural talent for computer programming. He soon finds himself working for a big corporation, Webscoe Industries. Dissatisfied with the low amount of money he receives for his first week's pay (less than $150 after taxes), he comes up with an idea after a talk with a co-worker about the various half-cent amounts in the company's payroll plan. After hours, Gus creates a program from which he embezzles $85,000 from his new employer's payroll (which is an early computer hacking technique known as salami slicing). Gus is brought to the attention of the CEO, Ross Webster (Robert Vaughn) after he shows up to work in a brand new Ferrari. Webster is a megalomaniacal billionaire obsessed with the computer's potential to aid him in his schemes to rule the world financially. Joined by his stuffy sister and right-hand woman Vera (Annie Ross) and his "psychic nutritionist" and mistress Lorelei Ambrosia (Pamela Stephenson), Webster blackmails Gus into helping him.Meanwhile, Clark Kent has convinced his newspaper editor Perry White (Jackie Cooper) to allow him a week's vacation to return to Smallville for his 15th high school reunion. Lois Lane (Margot Kidder) however plans to leave on her own vacation to Bermuda. En route with Jimmy Olsen to Smallville, Clark (as Superman), extinguishes a fire in a chemical plant containing vials of Beltric acid that can produce clouds of corrosive vapor when super-heated. However, Jimmy is injured with a broken leg while foolishly attempting to get photos of the disaster just as the fire crew realize their water supply is inadequate. To help put out the fire, Superman flies to a nearby lake and freezes the top layer with his super-breath, then carries the frozen sheet of water to the chemical plant where it melts and douses the fire.At the Smallville High Class of 1965 reunion, Clark Kent sees many old classmates, including football star Brad Wilson (Gavan O'Herlihy), his former bully who is now the town drunk and works as a local security guard, and cheerleader Lana Lang (Annette O'Toole), who is now the mother of a ten-year-old boy named Ricky (Paul Kaethler). Clark and Lana dance and quickly fall back into a comfortable ease with each other. Clark confesses that he has not been to Smallville since his mother's funeral, while Lana confides that her husband, Donald White, who was the student council president, left her and Ricky after just three years of marriage. Lana, who works as a secretary, recently had to pawn her engagement ring to pay bills and tells Clark she needs to get out of Smallville. He suggests she come to Metropolis and offers to help her find work.After the reunion, Clark accompanies Lana and her son to the Smallville bowling alley. When young Ricky does poorly at the game, Clark uses a burst of his super-breath to help him score a strike.Meanwhile, Webster schemes to monopolize the world's coffee crop. Infuriated by Colombia's refusal to do business with him, he orders Gus to command an American weather satellite named Vulcan to create a hurricane to decimate the nation's coffee crop. Gus travels to Smallville and in the evening arrives at a Webscoe subsidiary Wheat King office, (bribing Brad with liquor and waits until he passes out). Gus then carries out his boss's plan. After some funny problems with trying to turn on the computer involving putting both computer keys in at the same time, Gus reprograms the Vulcan weather satellite to cause torrential rains and tornadoes in Colombia.Clark takes Lana and Ricky on a picnic in a wheat field. However, when the boy disappears, Clark spots him unconscious as a harvesting combine approaches. Changing into Superman, he flies to the boy's rescue. When an excited Ricky tells Clark Superman had shown up, Clark brushes it off, saying that in Metropolis, he sees Superman every day. Ricky asks if Clark can get his hero's autograph.Webster's scheme is thwarted when Superman neutralizes the tornado and saves the harvest. Webster then orders Gus to use his computer knowledge to create kryptonite, remembering Lois Lane's Daily Planet interview from Superman years ago (from the first Superman movie), during which Superman identified it as his only weakness. Gus uses a computer to order the Vulcan satellite to locate Krypton's debris in outer space, but after the computer fails to analyze an "unknown" element in kryptonite (making up only 1% of the meteor), he improvises by replacing the unidentified element with tar, garnered from a pack of Camel cigarettes that he smokes.Meanwhile, Clark Kent returns to Metropolis to the Daily Planet newspaper write his story about the reunion when Lana telephones saying that Ricky bragged to his friends that Superman was going to be at his birthday party in a week. Clark assures Lana that he and Superman are close friends and he will make sure Superman is there for the party.A week later, Ricky's birthday party is transformed in to a huge ceremony at which the mayor of Smallville gives Superman the key to the city, partly for stopping the chemical plant fire. Gus and Vera, disguised as United States Army officers, show up during the ceremony and give Superman the man-made kryptonite as a gift, and are dismayed to see that it appears to have no effect on him.However, a little later at Lana's house, Superman feels dizzy. Lana receives a call that a tractor-trailer truck has wrecked and the driver is trapped, hanging off a bridge. She urges Superman to go rescue the driver. Superman promises to get to it later, then starts flirting with Lana. She insists he help the driver, snapping him out of his daze. He flies to the scene where the truck has already fallen off a bridge, though the rescue team was able to haul the driver out in time. Superman seems bewildered that he arrived too late. The synthetic Kryptonite had a delayed effect and Superman's personality takes a dark turn. In the following days, he engages in mean-spirited pranks such as blowing out the Olympic flame and straightening Italy's Leaning Tower of Pisa. The media covers the Man of Steel's altered behaviors and United Nations votes to censure Superman. 'Bad Superman' also becomes scruffy-looking as his bright blue and red suit becomes transformed into more of a maroon, dark blue color and he doesn't shave.With Superman distracted, Webster furthers his plans by controlling the world's oil supply. Gus moans that Ross gets his own way all of the time and that he feels unappreciated. Webster asks what Gus wants. Gus gives Webster a series of crudely drawn blueprints for a supercomputer, one with advanced defenses designed to find an enemy's greatest vulnerability. Ross makes a deal with Gus, agreeing to build his supercomputer in return for sorting out the oil tankers. Gus sends orders to all of the oil tankers to sail to the middle of the Atlantic Ocean and have them sit there until further notice and to command all the oil pumps to stop pumping.However, a British oil tanker does not follow instructions and continues to Metropolis. Lorelei meets the personality-altered Superman on top of the Statue of Liberty in New York City who flirts with her. Before Lorelei will do anything with him, she insists he stop the rogue oil tanker, so he flies to the tanker, punches a hole in its hull and causes a massive oil spill in the ocean.Meanwhile, Lana and Ricky arrive in Metropolis where Superman assuages his depression with a drinking binge. He is eventually overcome by guilt and undergoes a nervous breakdown after Ricky calls out to him, urging him to fight against his descent into evil. After nearly crash-landing in a junkyard, Superman splits into two personas: the evil, selfish, corrupted Superman and the moral, righteous Clark Kent. They engage in an epic battle across the junkyard, with the evil Superman repeatedly trying and failing to kill Clark by crushing him in industrial equipment. (They are both seemingly matched as Superman, despite his powers, becomes more physically weakened after using them, while Clark still has his superhuman strength, but none of Superman's powers of flight or heat vision).Superman finally knocks Clark unconscious and puts him on conveyor belt to be shredded. The battle ends when Clark bursts through the walls of the machine crusher and strangles his evil identity, vanquishing him for good. As a battered but unbowed Clark gazes up at the sky, he pulls his shirt open to reveal his emblem. Restored to his normal heroic self, Superman sets off to repair the damage his evil counterpart had caused. He flies to the oil tanker, blows all the oil back into the tanker with his super-breath and patches the hole with his heat vision.Superman then goes to the apartment penthouse of Webster to confront him only to find a video message from Vera that they are hiding out in Utah's Glen Canyon, the location where Gus Gorman's supercomputer has been built.After riding on mules to a crest ridge, Webster, Vera, and Lorelei take "air bikes" down to the canyon floor, sans Gus who decides to ride down by his own mule. Webster, Vera, and Lorelei arrive at a large cave where the supercomputer is and set out to await Superman's arrival. They activate the computer's system and begin to prepare it's built-in defenses.Superman flies toward the canyon and meets the supercomputer's missiles head on, eventually destroying them all. The last missile is an "MX" that stops him temporarily, however, he continues on, finding the cavern where Webster and his crew are hidden. Superman confronts Webster, Vera and Lorelei, and is forced into a battle with Gus Gorman's supercomputer, which severely weakens him with a kryptonite ray. Gus, guilt-ridden and horrified by the prospect of "going down in history as the man who killed Superman", destroys the turret projecting the beam with a firefighter's ax, whereupon Superman flees. The living computer becomes self-aware and begins to defend itself against Gus' attempts to disable it, draining power from electrical towers, causing massive blackouts across the North American continent.Ross and Lorelei escape from the control room, but Vera is pulled into the computer and forcibly transformed into a cyborg. Empowered by the supercomputer, Vera attacks her brother and Lorelei with beams of energy. One of them pins Lorelei to the cave's wall, the other acts like a death ray, seemingly to kill Ross himself.Superman returns to the battle with a canister of the Beltric acid from the chemical plant he saved earlier. After battling the living computer which attacks him with bolts of electricity and energy rays, the intense heat emitted by the machine causes the small canister acid to turn volatile, splashing on circuit boards and wires, eventually destroying the supercomputer and saving everyone.Superman flies away with Gus Gorman, leaving Webster and his cronies behind to deal with the authorities. After dropping Gus off at a West Virginia coal mine, where he gives him a job reference (which Gus declines and decides to slip away to re-start his life elsewhere), Superman uses his strength to crush a piece of coal into a large diamond. He returns to Metropolis and after reassuming his Clark Kent identity, reunites with Lana Lang, who has relocated to the big city with her son Ricky and found employment as Perry White's new secretary. At the Daily Planet, Lois Lane returns from a three-week vacation in the Caribbean where she uncovered a corrupt government scheme. Lois meets Lana Lang, who is working for the Planet, for the first time, but becomes jealous learning that the diamond Lana is wearing came from Clark.In the final scene, during a lunch break, Clark (as Superman) flies to Italy to correct one final problem he made as Bad Superman. He pushes the Pisa tower back into its original place... much to the dismay of a local vendor who is now selling straightened Pisa towers.