Following Avengers: Endgame, Wanda Maximoff and an alive Vision are living in Westview in a sitcom like scenario. However, it quickly becomes apparent that things are out of place in the town. It is revealed that Wanda, grieving over the death of Vision, unleashed her magic and created a giant reality bubble around the town (later called "the Hex"). During this process, she also used a piece of the Mind Stone that she has inside her and she recreated Vision, who has no memories of his life before Westview. The townspeople are slightly aware of what is happening, but have had their will removed and can only operate at Wanda's unconscious command. Each episode, the decade changes inside this reality, as it constantly shifts into different eras of classic sitcoms. Eventually, Wanda finds herself pregnant and she soon gives birth to twin children, Tommy and Billy.
Meanwhile outside the Hex, FBI agent Jimmy Woo and S.W.O.R.D. agent Monica Rambeau try to figure out what is happening with the town. Monica briefly enters the Hex, but is kicked out upon Wanda discovering her true identity. Director Tyler Hayward and an entire team, including the scientist Dr. Darcy Lewis, are brought in to try and decipher the issue. While Hayward plans to use lethal force to take down Wanda, claiming that she stole the Vision's body from S.W.O.R.D. HQ, when in reality, she left it behind. Jimmy, Monica and Darcy rebel and plan to rescue her and find a solution to her problem.
Vision slowly begins to become suspicious of the town and figures out that Wanda is controlling everything. However, before he can get a straight answer from her, a man claiming to be her brother Pietro, but with a different face, arrives to stir up trouble. While this briefly calms Wanda, she manages to see through his ruse. Later, when Vision attempts to leave the Hex to seek help from outside, he starts to disintegrate, which is sensed by Billy. Upon hearing from her son that Vision is dying outside the town, Wanda expands the Hex to save her husband, swallowing many S.W.O.R.D. agents and Darcy. Darcy meets up with Vision to tell him his history while Monica breaks through the Hex's barrier again, which at this point has altered her DNA enough to give her enhanced abilities. Eventually, Wanda's neighbor Agnes, reveals herself as a fellow witch named Agatha Harkness who has been monitoring her and trying to find out how powerful she is.
Hayward unleashes his ultimate weapon, a white colored Vision, which is a reconstruction made with Vision's original body. A large fight breaks out with Wanda battling Agatha, Vision battling Vision, and Billy, Tommy and Monica battling S.W.O.R.D. Vision manages to reawaken Vision's original memories and he flies away while Darcy arrives in the nick of time to capture and arrest Hayward. Agatha plots to absorb Wanda's power, which is revealed to be chaos magic, and is she also reveals that Wanda is the prophesized Scarlet Witch. However, Wanda overpowers her and strips her of her powers before transforming her into Agnes until she might need her again.
Having accepted that her new life was harming the residents of the town, Wanda removes the Hex and has one last emotional goodbye with her family before leaving Westview. Later, Monica meets with a Skrull agent about a potential future mission that will take her to space. Meanwhile, Wanda has relocated to a cabin in the wilderness to study Agatha's book, the Darkhold, in an effort to rescue her children.