WARNING: The following article contains major spoilers for Doomsday Clock #12 by Geoff Johns, Gary Frank Brad Anderson, Rob Leigh and Amie Brockway-Metcalf, on sale now.
Over two years since it started bringing the DC Universe and the world of Watchmen together, Doomsday Clock has finally come to an end with the final meeting between the iconic characters of the two comic book universes. The oversized final issue of the series lays out the series' mission statement and leaves both universes reshaped profoundly by the encounter, leaving plenty of room for new stories in both worlds. The complex narrative of Doomsday Clock ends with an equally complex finale that's in keeping with the meta-textual nature of the overall story and the cyclical nature of DC Comics and the wider superhero genre.
One of the much-heralded meetings before the series even started was between DC's flagship character Superman and Watchmen's omnipotent figure Doctor Manhattan. Manhattan had been haunted by visions of a future confrontation between the two, with a bloodied Superman apparently punching him followed by an impenetrable wall of darkness, with Manhattan unclear if this signals his own destruction or the end of all reality due to the two powerful forces colliding.
This confrontation is preceded by the culmination of the Superman Theory, a global conspiracy that the United States had secretly been creating its own army of meta-humans for years due to the high concentration of superheroes active in North America. Previous issues revealed that the widespread theory had taken the world by storm, resulting in mounting tensions and threats of war against the United States Led by foreign-backed figures including Black Adam of Khandaq.
Superman stands alone in Washington, D.C. fighting the product of this global tension that had been simmering since the opening, before confronting Manhattan after he reveals himself and admits he is responsible for the death of Jonathan and Martha Kent due to his tampering with the DCU's reality to create the New 52 to better shape the universe to his will.
When this prophesied moment comes to pass, Superman defends Manhattan from an attack, despite the shocking revelation about Jon Osterman's role tampering with his life. The moment is a profoundly inspiring one for Doctor Manhattan, as he finally understands that Superman embodies the hope and truth that lies in the heart of the DCU. The idealistic, aspirational nature of superheroes that the Man of Steel represents reminds Jon of his lost humanity, along with the picture of his old girlfriend Janey that he has kept with him decades after his transformation.
With this realization, Manhattan reinstates Alan Scott's discovery of a Green Lantern that made him one of DC's first heroes. This action also restores the Justice Society of America who inspire a teenage Clark Kent to become Superboy and save his parents from a car crash that would've otherwise killed them. The adventures of the teen Superboy subsequently inspires the creation of the Legion of Super-Heroes in the 31st century, with both teams arriving to help Superman turn the tide against the assembled enemies.
With the two teams restored and help Superman save the day, Manhattan can see the full past, present and future of the DCU, even beyond his meeting with Superman. Manhattan had previously observed that the DCU shifts every time Superman's origin is updated and revised and understands that the Metaverse is driven by hope; Superman is the embodiment of hope. Manhattan sees centuries of the Superman myth retold for future generations, with crossovers and reboots of the DCU previously unseen in its eventual future and eventually designated as new worlds in the DC multiverse.
As for the Watchmen characters, Manhattan summons them all to assemble at the Washington Monument, where Ozymandias is gunned down by the Comedian in retribution for killing him in the classic story. Before Blake can similarly kill Mime and Marionette, Lex Luthor appears and uses a vibrational frequency device to transport the Comedian right back to the moment of his eventual death in Alan Moore and Dave Gibbons' original series. Meanwhile, Ozymandias is saved by Reggie Long, the new Rorschach, whose faith in his superhero work was restored by Batman. After saving the life of his father's killer, Ozymandias is imprisoned for his crimes.
Before departing for his home universe, Manhattan pays one last visit to Carver Colman, an actor from Hollywood's Golden Age who died tragically when an attempt to blackmail him over his concealed homosexuality went horribly wrong. Having witnessed Superman's example, Manhattan urges Carver to be open and honest with himself, with news footage Carver eventually came out of the closet and had a celebrated film career and loving partner before his death decades later of natural causes.
With that, Manhattan returns to his own universe and apparently makes every nuclear weapon in the world disappear. While he leaves Mime, Marionette and their unborn daughter in the DC Universe, Manhattan takes the couple's son as the eventual heir to his omnipotent power before he changes his own history to avoid the accident that transformed him, instead living out a happy domestic life with Janey.
Back in the DC Universe, Superman had been unusually haunted by his parents' deaths since the start of the series, even having a nightmare about their demise before Manhattan rewrote reality. As a possible reward for Superman's faith and inspiration, Manhattan changes history, and an older Jonathan and Martha visiting Clark and Lois in Metropolis as if they had never died tragically at all.
The final moments of the series return to Watchmen's world, specifically the marital home of the now-retired Nite-Owl and Silk Spectre is shown, with the couple living under pseudonyms reflecting Dan Dreiberg's inspiration Mason Hollis and with a daughter of their own. As a mysterious force removes all nuclear weapons from their Earth, they are greeted by a young boy with Manhattan's symbol on his forehead introducing himself as Clark, with Superman's influence spreading positively to the normally dark, gritty world of Watchmen in the denouement.