Gorr and his daughter, Love, the last of their race, struggle in a barren desert. Despite their prayers to their god, Rapu, Love dies. The god-killing Necrosword calls to Gorr, leading him to Rapu's lush realm. After Rapu cruelly mocks and dismisses Gorr's plight, he renounces the god, causing Rapu to strangle him. The Necrosword offers itself to Gorr, who kills Rapu with it and vows to kill all gods. Gorr is granted the ability to manipulate shadows and produce monsters but is cursed with impending death and corruption under the sword's influence. After Gorr kills several gods, Thor, who has joined the Guardians of the Galaxy,^{[N 1]} learns of a distress signal from Sif. He parts ways with the team and finds an injured Sif, who warns that Gorr's next target is New Asgard. Meanwhile, Dr. Jane Foster, Thor's ex-girlfriend, has been diagnosed with stage four terminal cancer. With medical treatment proving ineffective, she travels to New Asgard hoping that Thor's hammer Mjolnir, which was previously fractured by Hela,^{[N 2]} might heal her.

Due to an enchantment Thor unknowingly placed on it years earlier to protect Foster, Mjolnir reforges and bonds itself to her. Thor arrives in New Asgard just as Gorr's attack begins. Thor is surprised to find Foster wielding Mjolnir, but teams up with her, Valkyrie, and Korg to fight Gorr. The group thwarts Gorr, but he escapes, kidnapping several Asgardian children and imprisoning them in the Shadow Realm. The group travels to Omnipotence City to warn the other gods and ask for their help in creating an army. The leader of the gods, Zeus, is unwilling to help, thinking they can remain safe and hidden from Gorr in the City; he also believes that Gorr will not be able to achieve his stated goal of visiting the realm of Eternity, where he (Gorr) will be granted one wish, presumably to destroy all gods. As a security precaution, Zeus orders the group's capture to prevent them from exposing the City's location to Gorr. When Zeus injures Korg, Thor impales Zeus with his thunderbolt, which Valkyrie steals before they escape to confront Gorr in the Shadow Realm. On the way, Thor learns of Foster's cancer diagnosis, and the two rekindle their relationship.

The group arrive at the Shadow Realm but are unable to locate the children. Foster sees ancient drawings that depict Thor's battle-axe Stormbreaker as a way to summon the Bifrost to enter Eternity, and deduces the trap laid out by Gorr. She throws away Stormbreaker to prevent Gorr from accessing it. However, Gorr overpowers the group and threatens to kill Foster, forcing Thor to summon it back. Gorr successfully steals Stormbreaker and injures Valkyrie before a weakened Foster collapses.

Upon traveling back to New Asgard, Thor discovers that Foster’s Thor form is not allowing her body to naturally fight the cancer. Due to this, Thor travels to Eternity's altar alone, and using Zeus's thunderbolt, imbues the children with his power to fight Gorr's monsters while he battles Gorr. When Foster senses that Gorr is about to kill Thor, she joins the battle with Mjolnir to save him. They destroy the Necrosword, freeing Gorr from its influence, but the three are brought into Eternity's realm. With Gorr poised to make his wish, Thor implores Gorr to revive his daughter instead of destroying the gods. Thor then leaves Gorr to make his decision and attends to Foster, who succumbs to her illness and dies in his arms. Moved by their display, Gorr wishes for Eternity to revive