On Mars, Dr. Manhattan drops the photograph of himself and Janey Slater on the Martian soil and revisits various turning points in his life.
In August 7th of 1945, a sixteen-year-old Jon Osterman is in the middle of assembling a watch when his father, a watch-maker, shows him the news of the atomic bombing of Hiroshima. Confronted with the undeniable facts of the theory of relativity, the elder Osterman declares his profession outdated and throws his son's watch-making parts out the windows, urging Jon to instead pursue a career studying nuclear physics. Jon does so in which he attended Princeton University in 1948, and graduating with a Ph.D in atomic physics in 1958.
By 1959, Jon is employed at Gila Flats in Arizona, where experiments are being performed concerning the 'intrinsic fields' of physical objects. He meets Professor Milton Glass, his colleague Wally Weaver, and his love interest Janey Slater. During a trip to New Jersey, Jon and Janey visit an amusement park. There, Janey's watchbrand breaks and is accidentally stepped on by a fat man. Jon decide to fix the watch and finally consummate his relationship with Janey.
One month later, on August, shortly after his thirtieth birthday, Jon plans to give Janey the repaired watch, only to discover he has left it in his lab coat which is inside the intrinsic field experiment test chamber. When retrieving his coat inside the chamber, he is accidentally lock in. Once Professor Glass and the others found Jon, they are shocked and horrified. Glass tells John that the chamber's door has locked automatically and the generators have already began warming up to begin an experiment: removing the intrinsic field from cell block fifteen. Jon is locked in and the door cannot be open or override the countdown. Jon could only accept death and examines the watch he has put back together while his colleagues - except Janey, who cannot bear to see the last moment and flees the room - watch in horror as the countdown reaches zero. Jon is disintegrated in a flash of light.
A month later, a series of strange events occur at Gila Flats involving the apparitions of a disembodied human circulatory nervous system, a circulatory, and a muscled skeleton which last for seconds. The residents believed the facility to be haunted until on November 22nd, Jon returns as a tall, hairless, naked, blue-skinned man with incredible abilities. Jon return to his life with Janey, but remains somewhat emotionless and distant among his peers.
A year later, on February 1960, the American government recruited Jon as their military asset and touted him before the public as "Dr. Manhattan," the first super-hero. He is also provided with a costume which he grudgingly accepts, though he refuses to accept the icon design which is provided for him (this being a stylized orbital model of the atom). Instead, Jon chooses as his emblem a representation of a hydrogen atom, whose simplicity he declares to be something that kindles his respect; accordingly, he painlessly burns the mark into his forehead. Despite being considered America's greatest weapon, Jon wasn't able to prevent certain disasters such as the assassination of President John F. Kennedy, even though he is aware it is going to happen as he meets the President.
By 1966, during the first and only meeting of the Crimebusters, Jon fell in love with the then sixteen-year-old Silk Spectre, Laurie Juspeczyk, and bitterly ending his marriage with Janey. By 1970, Jon's true name is revealed to the public as his father had passed away in 1969 and there is no reason to conceal it.
In 1971, Jon was requested by President Richard Nixon in intervening in the Vietnam War alongside the Comedian. Within two months, the United States had won the war and forever tipping the balance of the Cold War in the West's favor. In 1975, Nixon proposed a new constitutional amendment that would allow the President to have an extended term in office. Amidst all this, Adrian Veidt publicly reveal his identity as Ozymandias and announcing his retirement from costumed heroics. Veidt invited Jon and Laurie to visit his Antarctic retreat Karnak. During a conversation between Veidt and Jon, the world have radically changed since the last fifteen years from quantum physics to transportation all thanks to Jon.
During the Police Strike of 1977, Jon and Laurie handled the riots in Washington, D.C. in which the former dispelled the rioters by teleporting them back to their homes. This caused two people to suffered heart attacks, but Jon was certain that more lives would have suffered from the riots. Following the riots, the U.S. government passed an emergency bill (the Keene Act) proposed by Senator Keene which made vigilantism illegal and exempting registered adventurers such as Jon and the Comedian. Laurie and Dan Dreiberg retired their identities of Silk Spectre and Nite Owl, while Rorschach remains active in which he respond his feelings towards compulsory retirement by leaving a note on the dead body of a multiple rapist outside police headquarters.
In 1981, Jon and Laurie settled at the Rockefeller Military Research Center where it was well-equipped for Jon's work. But Laurie felt they had lost their privacy. In 1985, Jon recalls walking in New York with Laurie and buying a Time magazine commemorating Hiroshima Week, and finally the events that lead him to leave for Mars.
Jon construct a giant, glass structure that rises from the soil while wondering if events had gone differently if he didn't become Dr. Manhattan. He then stands on the balcony of his structure to watch a meteorite shower.
