Superman is enjoying a typical afternoon. He saves a young boy who has climbed too high on a power line, teaches him and his friends a lesson about playing safe, has the people of Metropolis call out congratulations and encouragements as he flies past, and he spots a police chase. He stops the criminal's car and the police catch up a moment later, followed by Lois, who has to swerve to avoid hitting one the suddenly parked cop cars, causing her passenger to be thrown from the moving vehicle. Superman manages to catch the man before he falls to his death. Lois' passenger, Clark Kent, is visibly disturbed by the fact that he has just been saved by Superman, but the Man of Steel sees nothing wrong with that picture, nor does anyone else. Superman puts Clark down and offers Lois an interview that night on top of the Daily Planet building, calling it a date, before he flies away again. Clark tells Lois that he'll just walk home.
Later, after Superman saves a helicopter from falling onto the city, he notices that his skin appears to be flaking off, leaving his hands covered with white splotches. He receives a tap on the shoulder and turns around to see... Superman! The first Superman claims that this is impossible, that he is the real Superman, while the second one points out that if that's so, why is his make-up coming off, since the first's face is now flaking as well. This drives that Superman into a rage as he punches the other one, proving that even if he is a fake, he still is as strong as the real Superman. He begins to feels sick and falls to the ground, emerging from the shadows a moment later, completely covered in bone-white, chalky skin to fly away towards the mountains outside of Metropolis.
This freakish Superman arrives at a lab hidden deep in the mountains, opens the door and proclaims with increasingly slurred speech "I...Have...Problem!" From out of the shadows steps Lex Luthor! Lex is there with his bodyguard Mercy and a scientist named Dr. Teng. When Lex asks Teng the reason for their Superman's condition, Teng replies that the alien DNA was too hard to clone, and must be breaking down, causing this subject to become brain damaged as well as physically deformed. Teng says that they should destroy all the "others." Lex disagrees and tells Teng to learn from this mistake. When the sickly Superman asks who he is and what's going on, Mercy responds "You're Bizarro, that's what you are." This Bizarro-Superman goes into a rage, screaming that he is not a mistake, that he is Superman, before flying away.
Hoping to prove that he's Superman, Bizarro returns to Metropolis and tries to do some Super Good Deeds. He stops a wrecking ball from destroying a condemned building, almost killing a wedding party in the process, and puts back together one of those bridges that separate to allows boats to pass through, almost destroying a large boat in the process. The real Superman saves all those people.
That night, atop the Planet building, Lois waits for Superman, and Bizarro appears to fulfill they're date. Superman arrives and Bizarro attacks him, knocking the giant globe and Lois off the roof in the process. Superman catches the globe and reattaches it while Bizarro saves Lois and takes her to a fancy restaurant to eat, causing all the other patrons to flee in terror. Lois is scared but thinking clearly, takes out her tape recorder and records her conversation with Bizarro. He claims that he must be the real Superman, because he remembers things like the Laboratory in the mountains. Lois asks about that Lab and Bizarro takes her there. Superman later finds Lois' tape recorder with the conversation about the lab and follows after them.
As they enter the laboratory, Lois finds to her horror as many as 8 large tubes, each containing a hibernating Superman-Clone. Lex appears, and reminds Lois of the time Superman fought Lex's robot Tyrannosaurus while in the same room as Kryptonite, which allowed Superman to bleed. Lex's men collected the samples and they've been working on making their own Superman ever since. Bizarro freaks out at that idea that he might really be a clone, and Dr. Teng shoots him with a powerful electrical net, forcing him to his knees. Lex admits that all the clones would probably develop the same problems as Bizarro, and tells Dr. Teng to initiate the Lab's self-destruct, which will happen in two minutes. As Lex is distracted offering Lois safe passage out, Bizarro attacks Lex, and begins wrecking the lab, causing it to collapse. Superman arrives and subdues Bizarro with force. Lex tells Superman that they must all hurry and get out of there, as they are sitting on half a kilo-ton of explosives, and Lex reckons that would take out Superman too. As Superman and Bizarro fight, Lex and Teng escape. Lois is injured trying to get out, and Superman turns his back to Bizarro to save her. Bizarro recognizes that only the true Superman would risk his life to save Lois. As the Lab begins to collapse, Bizarro holds up the falling roof long enough for Superman to get Lois out of there, saying "You am Superman. Superman save Lois." They manage to fly out before the Lab goes up in a huge explosion.
As they fly back to the city, Lois asks Superman if Bizarro might have survived that blast. Superman says he doesn't know, that he's never been in an explosion that bad before, but that he hopes Bizarro is still alive, as he had a good heart. "Of course he did," says Lois, "He came from good stock."