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Wanda Maximoff and Vision have just moved to Westview, a small town that looks straight out of a black-and-white 1950s sitcom, laugh track included. She has powers, he's a synthezoid, and they try to pass as a normal couple in front of the neighbors, especially nosy Agnes. Every episode the show jumps a decade, with a new opening and style: the '60s, the '70s, the '80s. But there are glitches: a voice on the radio calls out to Wanda, a beekeeper climbs out of a manhole, and the townspeople sometimes seem stuck in a script.
Outside town, S.W.O.R.D. is investigating a hexagon-shaped barrier, the Hex, that has swallowed Westview. Captain Monica Rambeau, freshly back from the Blip, goes in and becomes a character, Geraldine. Wanda gets pregnant and gives birth to twins, Billy and Tommy. When Geraldine mentions Ultron and Pietro's death, Wanda throws her out of town. FBI agent Jimmy Woo and scientist Darcy Lewis find that the Hex is broadcasting a TV show called WandaVision. S.W.O.R.D. director Tyler Hayward only cares about recovering Vision's body, which he keeps in pieces.
It becomes clear that Wanda, in her grief, created everything: the house, Vision and the lives of the residents, who are suffering trapped inside. Vision tries to leave, nearly comes apart, and Wanda expands the Hex to save him. A "Pietro" with a different face shows up at the door. Monica crosses the barrier again and gains powers. And Agnes is revealed as Agatha Harkness, a centuries-old witch who has been pulling strings the whole time.
Agatha forces Wanda to relive her past and learns she had magic as a child, amplified by the Mind Stone. It's chaos magic, and Wanda is the Scarlet Witch. S.W.O.R.D. reactivates Vision's original body, now white. The two Visions fight, and the White Vision recovers his memories and leaves. The fake Pietro was Ralph Bohner, a resident under Agatha's control. Wanda beats Agatha with runes and traps her in the Agnes persona.
Wanda takes down the Hex knowing she'll lose Vision and the boys, and says goodbye to them at home. Hayward is arrested. Monica gets a message from a Skrull. In the last scene, Wanda secretly studies the Darkhold and hears her sons calling for help. That comes back later.