Full story
In 5000 BC, a ship brings ten immortal beings to Earth, the Eternals: Ajak, their leader, Sersi, Ikaris, Kingo, Sprite, Phastos, Makkari, Druig, Gilgamesh and Thena. The Celestial Arishem sent them to hunt the Deviants, monsters that prey on humans. In 1521, after wiping out the last Deviants, the group splits up and each goes their own way.
Today, Sersi lives in London with Sprite, who looks like a child forever, and dates a human, Dane Whitman. A Deviant attacks the three of them, and Ikaris, Sersi's ex, shows up to help. The monster seems stronger, as if it's evolving. The trio flies to South Dakota and finds Ajak dead. Sersi inherits the link to Arishem and learns the truth: Celestials plant seeds inside planets, and every birth destroys the world it happens on. The Eternals' real mission was to let Earth's population grow big enough to feed Tiamut's birth. With half of humanity back after the Blip, the Emergence is days away. And the Eternals are machines; their memories are wiped after every mission.
Sersi decides to save Earth and gathers the group from around the world. Kingo has become a Bollywood star. Phastos has a husband and son in Chicago and carries guilt over giving humans the technology that led to Hiroshima. Thena suffers from a mental illness that Gilgamesh helps keep in check. In the Amazon, where Druig lives with a tribe he keeps under mind control, the Deviants attack and their leader, Kro, kills Gilgamesh. Phastos proposes the Uni-Mind: pool everyone's power into Druig so he can put Tiamut to sleep.
Then comes the betrayal. Ikaris knew everything, and he led Ajak to her death because she wanted to save humanity. Sprite, in love with Ikaris for centuries, takes his side. Kingo agrees with Ikaris but refuses to fight his friends and walks away. At the volcano in the Indian Ocean where Tiamut will rise, the fight breaks out. Druig knocks out Sprite, Phastos pins down Ikaris and Thena kills Kro. Since they can't put Tiamut to sleep, Sersi tries to turn him to stone. Ikaris moves to kill her but can't, because he loves her. He and Sprite join the Uni-Mind, and Sersi petrifies the Celestial with its hand rising out of the sea.
Crushed by guilt, Ikaris flies into the Sun. Sersi turns Sprite human so she can finally grow up. Thena, Druig and Makkari leave on the ship to warn other Eternals. Dane starts to reveal a family secret, but Arishem pulls Sersi, Phastos and Kingo into space. He will read their memories to decide whether humanity deserves to live. In the mid-credits scene, Thena, Makkari and Druig meet Eros, Thanos's brother, and Pip the Troll. In the final scene, a voice asks Dane if he is ready to wield the Ebony Blade. All of it is left open.

