SynopsisThe crisis at The Cube is stopped thanks to the Avengers. Before they can celebrate however, the Gamma villain the Leader unleashes a second gamma dome, projected from the center of Las Vegas, expanding far more quickly than the original. Most of the Avengers and several agents of SHIELD are caught in the Gamma-shield and are instantly mutated into horrible, mindless monsters under the control of the Leader. Only Thor is unaffected by the radiation, due to his Asgardian nature, but soon his teammates attack him in blind, animalistic rage and overwhelm him.
Hawkeye, en route to the Cube carrying a captured Black Widow with intentions to deliver her to the Avengers, is barely able to escape the effects of the gamma-shield himself. Just as he and Black Widow are about to continue their earlier battle, they catch a global broadcast by the Leader.
The gamma villain announces that the dome that started over Las Vegas is not a threat, but a promise that he will transform the entire world using gamma radiation to better reflect his image, that the faults and short-comings of humanity will no longer matter. Eventually, the entire world should be covered in the dome and the entire world under the control of the Leader. After capturing the Black Widow for a second time, Hawkeye considers the situation and can only think of one solution: Bruce Banner must be found. Leaving the Widow behind to be transformed by the approaching gamme dome, Hawkeyes hurries to where the Hulk was last seen, Northern Canada.
In Las Vegas, Thor and Doc Samson are brought to the headquarters of the Leader as the two survivors of the initial wave who were not transformed. Soon, Thor is forced to battle the Abomination as a form of entertainment for the Leader, as well as to keep him busy. Separated from his magical hammer Mjollnir, Thor is at a serious disadvantage.
In Canada, the Hulk is being hunted down by one of General Ross' Hulkbuster units. Their attempt to apprehend their target is interrupted, however, when Hawkeye arrives. Despite Hawkeye saving his life, the Hulk is not interested in offering a helping hand, especially when Hawkeye informs him that it is Banner that he needs, not the Hulk. By making the Hulk laugh, Hawkeye is able to cause the Hulk to relax enough to revert to Banner, who immediately wants to know the full situation.
At the Cube, the Wrecking Crew, once again enhanced by the Leader gamma-boosters, attempt to lift the hammer Mjolnir with no success. Eventually the hammer lifts itself and flies into the sky, returning to the one worthy to wield it. It arrives in the hands of Thor just in time for him to fight back against the Abomination, giving him the full strength of an Asgardian god. Unfortunately, that too turns out to be a ruse of the Leader, as it allows Absorbing Man the opportunity to emulate the magical head of the hammer and giving him the powers of Thor. Now Thor is again forced to fight, this time against both the Abomination and the powered up Absorbing Man.
In Canada, Banner is able to locate the epicenter of the gamme dome's expansion to the Leader's base in Las Vegas. He also inoculates Hawkeye, making him temporarily immune to the dome's effects. Then, after transforming back into the Hulk he leaps through the air towards the source of the dome with Hawkeye clinging to his back.
The pair reach the Leader's lair just as Thor and Absorbing Man's fight spills into the streets of Vegas. The Leader says he was expecting the Hulk to arrive, but suggests he consider a world of nothing but gamma creatures, a world where the Hulk is not a monster, but fit to be a king. Hulk seems unmoved by the suggestion, as the Abomination attacks him.
Hawkeye, meanwhile, is forced to battle the gamma-mutated Avengers. During the fight, Hawkeye reveals that he Banner created a new set of arrows from him that give a dosage of the same inoculation that keeps him from becoming a gamma mutant. Once the Avengers are shot with them, they are cured and freed of the Leader's control but also knocked unconscious. The Leader, seeing that he now must battle the Hawkeye alone while his minions are busy, reveals his final weapon: a giant battle robot suit.
In his battle with the Absorbing Man, Thor is able to concentrate enough so that he can control the very material that his foe is made of; after all, Mjolnir is his to control. Likewise, with Hawkeyes help, Hulk is able to best the Abomination. With all of the Leader's threats resolved, the Hulk is able to focus on destroying the gamme dome emitter, causing the dome to evaporate and all the victims of gamma mutation to finally revert back to their natural forms.
SHIELD is able to take the Leader and the Absorbing Man back into custody, while Clay Quartermain is able to use footage provided by Hawkeye to clear the archer's name of any wrong doing, and also label the Black Widow as a HYDRA double agent. Hawkeye rejects both the Avengers and SHIELDs offers for membership, stating that he is better off on his own trying to hunt down the Widow. At the same time, Hulk is offered membership back into the team. He agrees to return...under the condition that "Cupid" stays. Hawkeye, clearly baited by the insult, agrees to join as well.
Meanwhile, in the Nevada desert, Abomination is the only member of the gamma villains to escape the grasp of SHIELD. There, he is greeted by the growing number of super villains that have formed a dangerous alliance: Baron Zemo, Amora the Enchantress, Skurge the Executioner, Simon "Wonder Man" Williams and the Crimson Dynamo. The Masters of Evil.
"Gamma World" originally premiered as a special hour long episode in October, 2010. It was later split in two normally-sized 30-minute episodes for future airings.
In an interview, Story Editor Christopher Yost confirmed that some ideas in the "Gamme World" story were based on plans for the cartoon series Hulk: Gamme Corps. Gamma Corps was canceled during pre-production, largely due to Marvel deciding to produce a show focused on the Avengers and the wider Marvel Universe instead.