Thanos managed to disappear half the life of the universe, the long-awaited balance was achieved; on earth, all the inhabitants who managed to survive being submerged in deep depression and enormous grief, including our heroes.
The terrible Titan not only devastated part of the population of the earth, but also managed to destroy the gems of the infinite so that their actions were irreversible, there is no going back, there is no solution, Thanos has won and the Avengers could not do anything.
Natasha along with the survivors Rhody, Carol Danvers, Nebula, and Rocket, try to protect and maintain order on earth and the universe; while Capital Steve Rogers has become a citizen who provides moral support to the victims of the click; On the other hand, Thor founded a small town called Asgard on the shores of Norway, and leads a quiet life hidden in anonymity.
Clint Barton, who used to be Hawkeye, has become a kind of avenger and has lost control after the disappearance of his family during that terrible holocaust.
Grief, resignation and sadness, are the feelings present on earth, life goes on, but nothing is the same; a day like any other, in an abandoned car parking lot, a rodent walks the dash of the van that belonged to Luis, in which Dr. Hank Pym installed a machine that allows traveling to the quantum kingdom; accidentally the rat activates the controls and allows Ant-Man to return to this reality.
Disoriented for not knowing what is happening, he starts looking for information and finds out those five years have passed since the terrible tragedy that the universe suffered at the hands of Thanos; He immediately goes to his daughter's house, which fortunately survived and is alive.
Scott travels to the central Avengers command in search of answers, where he will be received by Steve and Natasha; who explain everything that happened; but Ant-Man not only brings questions, it also brings little hope to reverse this whole terrible situation; Lang explains that his stay in the quantum kingdom did not exceed five hours, while five years passed in this dimension.
This explains that in the quantum kingdom many things are relative, such as space-time, and that perhaps through that theory they could reverse Thanos' terrible snap; but only a brilliant mind could decipher the way to do it and unfortunately Dr. Pym also disappeared, so there is no alternative but to resort to an old acquaintance.
They visit Tony, who leads a quiet and family life with his wife Pepper and daughter Morgan, they propose Scott's theory about the quantum kingdom, but he immediately replies that temporary travel is impossible, there is no way to turn back time; however, Steve asks him to reconsider.
Given the refusal of Stark, they seek a second opinion, this time they look for Dr. Bruce Banner, who has been working with gamma radiation for five years and has managed to merge with Hulk, obtaining the best of both individuals.
When listening to Scott's theory, he warns that he does not possess the necessary knowledge in the field, but is willing to help in whatever is necessary in order to recover all lost lives.
Tony keeps thinking about Steve's approach, and after looking at a photograph with his pupil Peter Parker, who disappeared thanks to Thanos, decides to perform some calculations with his artificial intelligence assistant FRIDAY; surprisingly it is possible to jump in time through the quantum realm with proper guidance.
As the days go by, Tony shows up at Avengers base and explains to Steve what he has discovered; but it imposes some conditions to advise them in their mission; the number one will be to keep your present as it is, and the second is that you are not willing to risk your life.
The adventure of the most powerful heroes in the universe is about to begin, they must collect the six gems of the infinite again to reverse Thanos click and return the lives of all victims.