- Real name: Nathaniel Christopher Adam
- Current alias: Captain Atom
- Alias: Monarch, Allen Adam, Cameron Scott
- Affiliation: Justice League, Extreme Justice, Super Buddies, Living Assault Weapons, Monarch's Army, United States Air Force
- Identity: Secret
- Alignment: Good
- Universe: New Earth
- Gender: Male
- Hair: White, Silver, Eyes: Blue, Silver
- Status Citizenship: American
- First Appearance: Captain Atom #1 (March, 1987)
Captain Atom was Nathaniel Christopher Adam, a United States Air Force officer of the Vietnam War era. Adam had been framed for a crime he didn't commit and sentenced to death under the watch of Col. Wade Eiling in 1968. As an alternative to execution, he was invited to participate in a military experiment with little chance of survival, in exchange for a presidential pardon. The experiment involved testing the hull of a crashed alien ship's durability by exploding a super nuclear bomb under it. Adam survived as the metal melted into his body and the excess energy threw him forward in time nearly twenty years (not incidentally, this coating with alien metal gave the revised character a full-body silvered metal look distinctly different from his previous incarnations).
Regaining coherence in 1986, Adam found himself a man out of his time and in the hands of Eiling, now a general and the second husband of Adam's now-deceased wife. Everyone had assumed that Nathaniel Adam had died on the day of the experiment, so his presidential pardon was never issued and the current government refused to acknowledge the previous administration's promised pardon. Seizing the opportunity at hand, the government used the outstanding murder/treason charges against Adam to blackmail him into being a government-controlled superhero (codenamed Captain Atom). And in keeping Adam's true origin a secret, the government gave him a origin and he was assigned the alias of Cameron Scott, an Air Force intelligence operative. It was during this time he met the superpowered terrorist, Plastique, who would become a recurring part of Nathaniel's life.
Upon his initial return from the Quantum Field, Nathaniel Adam was the classic "man out of his time". Early conflicts involved him coming to terms with his lost time with his children (who were now close to his current age as a result of the time jump), the death of his wife (who had married his nemesis Eiling prior to dying), and the overall ramifications of his newly acquired powers.
Atom/Adam served under Eiling reluctantly, while succeeding in clearing his name. Eventually, Atom rebelled against Eiling, resigned from the Air Force and found some fulfillment as an actual superhero. Captain Atom joined the Justice League at the request of the U.S. government, eventually serving as leader of Justice League Europe. During his career, he had a brief romance with Catherine Cobert, developed a friendly "rivalry" with Firestorm, become involved with and eventually married to Plastique (ironically, a one-time Firestorm foe), battled Major Force (his would-be successor), learned basic heroics from Batman when he briefly lost access to the Quantum Field, and commanded the metahuman forces during the alien invasion of the Alliance.