What Happened to Paul Atreides's Sister?

In Frank Herbert's books, Paul's sister Alia Atreides became regent of his empire after he walked into the desert, was slowly taken over by the inner memory of her grandfather, Baron Vladimir Harkonnen, and killed herself by leaping from a window at the end of Children of Dune. In Denis Villeneuve's films she has not even been born by the end of Dune: Part Two, and her film story is still to come. (Children of Dune; Dune: Part Two)

The books: born awake#

Alia was born on Arrakis, some months after her father, Duke Leto Atreides I, was killed. While Jessica was pregnant, she drank the Water of Life to become a Reverend Mother of the Fremen, and the poison woke the unborn child too. Alia came into the world pre-born, with a full mind and the memories of every Reverend Mother before her. The Fremen found her unsettling. (Dune)

At the end of Dune she is still small. She is captured and taken before the Emperor and the Baron, and she kills the Baron, her own grandfather, with a gom jabbar as she tells him who she is. The novel's appendix notes that the Bene Gesserit called her the Accursed One. (Dune)

Dune Messiah: the priestess#

Twelve years into Paul's reign, Alia is fifteen and a high priestess of the religion built around her brother. She is drawn to the ghola Hayt, the restored Duncan Idaho, and she pushes her own spice use dangerously far chasing visions that are slipping away from her. At the end of the novel Paul walks blind into the desert after Chani dies giving birth to twins, and Alia is left to rule for his children, with the restored Duncan later at her side as her husband. (Dune Messiah; Children of Dune)

Children of Dune: the regent and the Abomination#

Nine years later, Alia rules as regent for the twins, Leto II and Ghanima. She governs through the priesthood and has grown hard and suspicious. Inside her, the crowd of ancestral voices has been fighting for control, and the loudest is the Baron. He offers to quiet the others in return for moments of control, and little by little he takes over. This is what the Bene Gesserit feared and named Abomination: a pre-born person possessed by the dead. (Children of Dune)

Under the Baron's influence, Alia turns on her own family. She plots against her mother Jessica, and she promises Ghanima in marriage to Farad'n Corrino. Duncan, sure she is lost, provokes Stilgar into killing him so that Stilgar will break with her. (Children of Dune)

Then Leto II returns from the desert, alive and changed, his body covered in sandtrout. He confronts Alia in front of her court, and her attempts to have him killed fail. In a moment of clarity she knows what she has become and that she can't drive the Baron out. She throws herself from a high window and dies. The Children of Dune explained page has the full plot. (Children of Dune)

The films: a different Alia#

David Lynch's 1984 film keeps Alia as a child. She lets herself be captured, cuts the Baron with the gom jabbar, pulls out the plugs of his suspensor belt, and he is sucked out of the hall into the mouth of a sandworm. The novel has no worm. (Dune (1984 film))

Villeneuve's Dune: Part Two keeps Alia in the womb. Jessica drinks the Water of Life while pregnant and talks to her unborn daughter, and Paul sees Alia only once, as a grown woman, in a vision. The film's short time span is why: the novel covers about two years. The Part Two to Messiah page sets the changes side by side. (Dune: Part Two)

Dune: Part Three, adapted from Dune Messiah and set 17 years after Part Two, gives Anya Taylor-Joy a full role as Alia. Speaking at the trailer launch, Taylor-Joy described a character who carries the wisdom of generations in her head and whose strongest feeling is her devotion to her brother. What happens to the film Alia after that is not yet known. (Dune: Part Three trailer launch)

Was Alia doomed?#

Our reading, and it is only a reading, is that the books mean her as the cost of the Atreides gifts. Leto II and Ghanima are pre-born too and survive it because they learn from what happened to her. Herbert makes Alia's fall a warning about the same power Paul had: too much of the past and the future in one head, with no one able to stop it. For her full life, see Alia Atreides. (Children of Dune)