"Hereafter" is the forty-third and forty-fourth episodes of Justice League. It first aired on November 29, 2003.
A group of supervillains are gathered around and plotting to take their revenge on Superman. They arrange an ambush for the Man of Steel by attacking Metropolis. They battle the rest of the Justice League, but when Superman arrives, Toyman reveals his secret weapon: a giant toy robot equipped with a disintegrator beam. Toyman fires several times, and sections of the city disappear without trace. Superman evades the beams, but Toyman takes aim at Batman and Wonder Woman. Superman throws himself in front of them, and takes the blast, disappearing without trace. Shocked, the League and the world must accept what seemed impossible: Superman is dead.
The only person who refuses to believe it is Batman. He analyzes the evidence from the battle, insisting that it is impossible for objects to disappear without a trace, citing the law of conservation of mass. He coldly snubs the invitations of Alfred and the other Leaguers to attend Superman's funeral in Metropolis.
At Superman's funeral, the attendants include the League (minus Batman), the staff of the Daily Planet, Jonathan and Martha Kent, several world leaders, superheroes, and, to Lois Lane's outrage, Lex Luthor. J'onn J'onzz pronounces a eulogy, and the League ceremonially inters a coffin in a monument.
Holding a wake for Superman in the Watchtower, the League swaps stories about him, then J'onn tentatively proposes adding a new member. Suddenly, Lobo crashes through the window, announcing that he's there to take Superman's place. When the League orders him out, he decides to "audition" by tearing the Watchtower apart and attacking them. They hold him off, then hear that dozens of supervillains are running amok in Metropolis, celebrating Superman's death in their own fashion. The League reluctantly bring Lobo along as they go to fight.
Investigating another of his theories, Batman follows a trail to Superman's memorial. Finding nothing, he wonders if he's wrong, and Superman really is dead. Alone, he addresses the monument, telling Clark that, despite their differences, he has always respected him, and that he will miss him… but his tribute is interrupted by a nearby explosion. Batman takes off to combat the attacking supervillains.
The League attacks, with difficulty subduing the rogue villains. Lobo makes himself useful in his own fashion, beating Kalibak into submission, though causing plenty of destruction in the process. To a downcast League, he exults, "when you got Lobo on your team, who needs Superman?"
The scene dissolves to a barren landscape, where Superman is seen, unconscious, under some rubble... and a red sun.
Superman regains consciousness, and sees the barren landscape, except for himself and sections of the Metropolis city that were hit by Toyman's disintegrator beam; wherever he is, the beam transported him there instead of destroying him. He sees that the sun is red, and his powers aren't working. He picks up a signal on his communicator, and decides to move closer to it. Salvaging what food and supplies he can from the cars in the street fragments, he then siphons gas into one of them, and drives off.
Making camp one night, he is menaced by a pack of wolf-like creatures. He attempts to scare them off, without effect, then manages to drive them away with fire. Realizing he is powerless, he uses tools from the car to fashion an iron bar into a crude but effective sword.
Before too long, his car is out of gas, and he is forced to walk. Attacked that night by the creatures again, he kills their leader, and subjugates the rest of the pack, harnessing them as sled dogs for a new improvised vehicle.
After a few more days, he reaches the ruins of a city, and finds the source of the signal: the Watchtower, crashed to the ground. Entering, he tries to access its computer; the computer tells him that the rest of the League's whereabouts are unknown, then shuts down due to low power. Superman bangs his fists down in frustration and asks aloud, "what happened to everybody?" A voice answers, "they died, Superman. Thousands of years ago." A figure appears from the shadows – Vandal Savage.
Savage seems uncharacteristically glad to see Superman, and he soon explains why: the planet they are on is Earth, 30,000 years in the future, and the entire human race, except for Savage, is dead. Only a few months after Superman disappeared, Savage developed a weapon that allowed him to control the force of gravity. Without Superman, Savage killed the rest of the Justice League, and proclaimed himself ruler of the world. But his newfound powers disrupted the balance of the solar system, killing the rest of the human race. Superman is initially enraged, but Savage says he's reformed: after millennia of loneliness and isolation, he's come to realize that his obsession with power was meaningless.
With plenty of time on his hands, Savage has built himself a luxurious mansion in the ruins of Metropolis, with a large garden and plenty of technological amenities. He passes his time reading, working on various inventions, or on hobbies such as restoring other parts of the city. He treats Superman to a home-cooked meal, and invites him to stay. Wandering around the mansion one night, Superman finds a time machine. He asks Savage why he did not finish it. Savage says there would be no point, as the machine would not allow him to travel back to any time where he was already alive. Superman points out that he can, since he's dead, and can stop Savage's destruction of the world.
He and Savage work together to complete the machine, but find that they can't keep the portal open without a much larger power source. Savage knows of only one: a zero-point energy generator that he built, but was stolen some years ago by a colony of giant cockroaches. He and Superman sneak into the colony to get it back. In battle with the roaches, Superman apparently falls to his death into the pit containing the generator – but instead, the device, which as Savage has explained is like a "miniature sun," instantly restores his powers, and he is able to get himself and Savage away safely.
Savage opens the portal, giving Superman the information he needs to thwart his younger self's plan. Before going, Superman asks what will happen to Savage if he succeeds. Savage tells him not to worry: "Do what you do best... save the world." The two men shake hands, and Superman departs.
Back in the present, while Lobo is crowing over Kalibak, Deadshot takes aim at Batman with a missile. Superman's hand appears and catches it. In wonder, the League crowds around him (except for Batman). Superman tells Lobo he's fired, and the bounty hunter angrily jets away on his bike. Superman says he'll explain what happened to him, but first they have a job to do. The League flies into action, with himself at its head.
In the future, Savage is sitting alone among the ruins of Metropolis. He sees a ghostly figure of a child run by, then more people. Slowly, the ruin disappears, and a living city replaces it, filled with people. Savage sees his own body slowly fade from existence, and says, "Thank you, my friend..."
- Prior to the premiere of Justice League Season 2, interviews stated that the team was to have a temporary addition. This episode, in which Superman was supposedly killed, would prompt the rest of the team to recruit a new member. Originally, the new member was to be Captain Marvel. However, legal rights prevented that appearance and Lobo was chosen instead as the least likely suspect.  When Superman investigates the fallen Watchtower, Aquaman's portrait is shown on the computer screen with the other founding members, indicating that the League eventually settled on him after Superman's death (or would have, had Superman not returned).
- When the League debates whether to add a new member to the team, the Flash proposes Aquaman; Green Lantern proposes Metamorpho; and Hawkgirl asks if Supergirl is old enough; Wonder Woman proposes offering Batman full-time membership.
- The attendants at Superman's funeral include Aquaman and Mera, Dr. Fate and Inza, Alfred Pennyworth, Tim Drake, Jonathan and Martha Kent, Lana Lang, Supergirl, Bibbo Bibbowski, Maggie Sawyer, Lois Lane, Jimmy Olsen, Perry White, Orion, Lightray, and a few members of the Green Lantern Corps (Larvox, Tomar Re, Katma Tui, Kilowog, and Kyle Rayner). Diana's mother, Queen Hippolyta, also appears by her daughter's side as she dresses for the funeral.
- This episode features many characters from Superman: The Animated Series, such as Livewire, Metallo, Volcana, and Lobo.
- Corey Burton replaced Bud Cort, Malcolm McDowell, and Miguel Ferrer as the voices of Toyman, Metallo, and Weather Wizard, respectively. Both Cort and McDowell would return to their roles in Justice League Unlimited.
- In describing his plan to Superman, Savage mentions stealing a piece of dwarf star matter from Ray Palmer, better known as The Atom.
- This is Vandal Savage's last appearance on the series. It is never explained exactly how the League stopped his plan, but the disappearance of his future self may imply that he died sometime between the present and the future.
- Several elements of the story are similar to the comics storyline Funeral for a Friend, including Batman watching Superman's memorial procession from a rooftop.
- Part II is reminiscent of Richard Matheson's novel I Am Legend, and its film adaptation The Omega Man, both depicting the life of a single man on Earth after the rest of humanity is wiped out by some disaster.
- Vandal Savage's fade in Part II is similar to the way the characters of the Back to the Future trilogy do so when time is altered.
The Flash: I used to be able to goof around so much because I knew Superman had my back. Now all I've got is his example, and that's gonna have to be enough.
J'onn J'onzz: Though we gather here today, bound together in sorrow and loss, We share a precious gift. We are, all of us, privileged to live a life that has been touched by Superman. The Man of Steel possessed many extraordinary gifts, and he shared them with us freely. None of these gifts were more remarkable than his ability to discern what needed to be done, and his unfailing courage in doing it, whatever the personal cost. Let us all strive to accept his gift, and pass it along, as an ongoing tribute to Kal-El of Krypton, the immigrant from the stars, who taught us all how to be heroes.
Batman: I've got some things to say. I should've said them when you were here, but... Despite our differences, I have nothing but respect for you. I hope you knew... know that. You showed me justice doesn't always have to come from the darkness. I'll miss...
(Superman is holding a rock over Savage's head after learning he wiped out the human race)
Superman: Self-help books? You don't seem the type.