In the midst of a Khund invasion, the city of Metropolis celebrates "Superman Day", a day of recognition for all the things Superman has done for the city. However, the Man of Tomorrow doesn't seem too enthusiastic about the festivities.

After he has destroyed a Khundian warship, Lois and Jon try to get Clark to come to a celebratory panel, which he does hesitantly.

The presentation begins with a group of guests recounting their experiences of when Superman saved them from various dangers. Meanwhile, Clark feels uneasy, worried about the Khunds sending out a larger force. As he uses his telescopic vision to check, though, he experiences brief, strange allucinations of ships, but then they disappear.

During the presentation, Lois is continually bombarded with calls from her boss, Perry White, but when he appears on stage to speak at the panel, Superman realizes that something is awry. He flies off, but is stopped by Wonder Woman, who reveals the truth: the Khunds indeed attempted a large-scale invasion, but the world's heroes have already taken care of it. Diana apologetically admits Martian Manhunter influenced Superman telepathically so he wouldn't notice anything, and Lois had actually been on the phone with Batman the entire time. Diana explains his family and friends did this because they wanted him to enjoy his day. After all, he also influenced all of them.

As Superman returns to the presentation, he sees the Super and Bat-Families, the Justice League, the Titans, the Earth's Green Lanterns... all the heroes, and even villains like Harley Quinn and Deathstroke gathered in celebration of him.

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On his birthday, Superman recounts the events that occurred right before his arrival:

After a night out on patrol, Superman is teleported into the lair of Vandal Savage, who hooks him up to a device that can "weaponize Hypertime". Vandal explains that the device will trap Superman in an endless time loop, where he will never be able to stop Vandal from taking over the world.

Vandal activates the device, sending the hero into his own past.

Superman awakens in 1930s Metropolis, where he finds himself battling a group of gangsters. Clark realizes that he is missing some of his powers, but is exhilarated none the less.[1] As the time loop progresses, Vandal throws Superman from adversary to adversary, including former villains, alternate versions of himself, and even the power of "nature" itself. Despite this, Clark doesn't back down. He uses time to his advantage, overcoming Vandal's attack, and besting the enemy once and for all.

As Clark returns home, he realizes that every incarnation of him would always end with him reuniting with his family.

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While Superman stops Brainiac from attacking Japan, Maggie Sawyer negotiates a hostage situation at a High school; a Principal has taken a student and is holding her at gunpoint.

Superman overhears the situation from afar, believing the Principal to be under the influence of Brainiac. The Police bring the Principal's wife to ease the situation, snapping him out of the villain's control. Superman severs the controls of Brainiac's ship, overriding the signal, freeing the principal.

Later, Maggie finds a homeless man and tries to help him, but he ignores her. The man is actually in the process of being controlled by Brainiac, but the connection fails.

As Superman leaves Japan, he realizes that Brainiac was doomed to fail because humanity is "too strong-minded" to be controlled by any higher power.

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Butch Matson takes his car to the shop to get it repaired. When the mechanic asks what damaged the car, Butch responds with "a man wearing red under-wear."

While he waits outside, Butch is visited by Superman, who confronts him about the night before. Clark tells him that he looked in to Butch's past, learning about his troubled childhood. Butch became an orphan, and ended up on the streets after both his parents died when he was 13. Butch remembers a hot day when him and the other orphans just wanted to swimming, but there was no pool.

Superman tells him to make a decision; either continue to cause trouble in the city, or "be the person who wasn't there for him".

Once Superman flies off, Butch takes his repaired car to the old orphanage and opens a fire hydrant, delighting the children, and fulfilling his inner conflict.

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Superman encounters Lex Luthor in the Smallville Planetarium, confronting him about acquiring two objects: the "Eye of Xotar", and "Chronos' Time Scissors". Together, these two objects could be used to erase any genealogical line from history. Luthor rebuffs the claims, stating that he only wishes to stargaze.

Superman asks why Luthor chose the Planetarium, and he responds by saying that it was the one place that offered him solace as a child. Luthor explains that in Smallville, there is a time between Winter and Spring where the weather becomes completely unpredictable, a time called "The Fifth Season". During this time period, Luthor would visit the Planetarium to escape from his father's abuse.

He then tells Superman of a time where he had once gone there in the hopes of using the facility’s telescope to send out a distress call into space, looking for someone to come down from the heavens to help him. Luthor believed his call was left unanswered, but he was wrong...

In school, Luthor had built a "rudimentary laser" with his lab partner, Clark Kent, and taken it to the telescope. However, he had forgotten to heat up the liquid nitrogen, which would have killed him if not for Clark Kent. Clark realized it, and used his heat vision to fix the mistake, saving his friend. Luthor never realized his call had been answered, at the very moment it was sent.

In the present, Luthor admits to planning to use the Eye and Scissors to kill Superman. Superman knows this, but wonders if things could be different between them.

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On Earth, five billion years in the future, the red sun expands to engulf the planet. Superman goes to visit his parents' gravesite and recounts how he won't let the planet be forgotten and updates the Kents on Lois who now runs a galactic information network and tells them that they would be proud of Jon. He says that he loves them, says good bye, and thanks them for all they did for him.

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Clark Kent is trying to get an article on political corruption ready in time for the next edition, but once and again he is derailed by emergences only Superman can take care of. Despite everything Clark manages to meet the deadline, but Perry White tells him it's old news now and he is to cover the latest Superman's deeds. As he leaves with Jimmy Olsen, Clark ponders superheroing and reporting are not so different.

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A tour guide welcomes a group of visitors to "Actionland", a Superman-themed park. The woman guides the crowd throughout Superman's life: his escape from Krypton, his childhood in Smallville, his adult life in Metropolis, his battles alongside the Justice League or by himself against his worst enemies until his final battle against Mister Mxyzptlk where the Man of Steel fell down.

All of sudden, the world around the guide tour falls apart, and Mister Mxyzptlk appears, grumbling about his inability to come up with a suitably epic ending despite his reality-rewriting powers. His girlfriend -and tour guide- Miss Gsptlsnz states Mxyzptlk can't choose on an ending because, deep inside, he doesn't want the story to end. Superman defines him as much as he defines Superman.

Mxy and Gsp hug as Bat-Mite and his partners-in-crime decide it's their turn now to ride Superman's rocket all the way to the Batcave.

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Superman spots a crook shooting an innocent bystander. As he streaks forward, he knows he'll not make it. He's too far away.

Nevertheless, the hostage woman leans her weight against the gun's barrel, catching the crook off guard. Her reckless behavior obviously doesn't stop the bullet but buys Superman the extra attosecond he needed to save her.

Later Superman is talking with Lois. His wife states people are inspired by Superman, but they inspire him in turn.

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Superman gets punched across several buildings and crashes into a coffee shop. Two women find his barely-conscious body and are trying to drag him to a safe place when his assailant arrives and rushes towards Superman. Suddenly Supergirl pounces on the axe-brandishing alien and hits him with a brutal combination of heat vision and rapid fisticuffs to the face. Furious, the alien gets her off him, roaring he'll deal with her next, and resumes his attack.

Superman engages him again, but the alien is too powerful and smashes him down once and again easily. Once he's pinned Superman to the ground and shot Supergirl down, the savage alien declares his name is Rogol Zaar, who cleansed the galaxy of the Kryptonian plague and has come there to exterminate the last survivors. As he drives his blade into Superman's chest, he declares he'll finally end the Kryptonian menace just like he promised Jor-El when he destroyed Krypton.

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