Following the destruction of House Atreides by House Harkonnen, Princess Irulan, the eldest daughter of Padishah Emperor Shaddam IV, secretly journals that Paul Atreides may still be alive. On Arrakis, Stilgar's Fremen troops, including Paul and his pregnant mother, Lady Jessica, overcome a Harkonnen patrol. When Jessica and Paul reach Sietch Tabr, some Fremen suspect they are spies, while Stilgar and others see signs of the prophecy that a mother and son from the "Outer World" will bring prosperity to Arrakis.Stilgar tells Jessica that Sietch Tabr's Reverend Mother is dying and that Jessica must replace her by drinking the Water of Life: a poison fatal for males and the untrained. Jessica transmutes the poison, surviving and inheriting the memories of every female ancestor in her lineage. The liquid also prematurely awakens the mind of her unborn daughter, Alia, allowing Jessica to communicate with her. They agree to focus on convincing the more skeptical northern Fremen of the prophecy. Chani and her friend, Shishakli, believe the prophecy was fabricated to manipulate the Fremen. However, she begins to respect Paul after he declares that he only intends to fight alongside the Fremen, not to rule them.Paul and Chani fall in love as Paul immerses himself in Fremen culture: learning their language, becoming a Fedaykin fighter, riding a sand-worm, and taking part in raids against Harkonnen spice operations. Paul adopts the Fremen names "Usul" and "Muad'Dib". Due to the devastating spice raids, Baron Vladimir Harkonnen replaces his nephew, Glossu Rabban, as Arrakis's ruler with his psychotic, murderous younger nephew, Feyd-Rautha. Lady Margot Fenring, a Bene Gesserit, is sent to evaluate Feyd-Rautha as a prospective Kwisatz Haderach and to secure his genetic lineage.Jessica travels south to unite with Fremen fundamentalists who believe in the prophecy. Paul stays North fearful that his visions of a holy war will occur if he goes south as a messiah. He reunites with Gurney Halleck, who leads him to the hidden atomic stockpile of House Atreides. Feyd-Rautha attacks the northern Fremen-including Sietch Tabr-forcing Paul and the survivors to journey south; Shishakli remains and Feyd-Rautha kills her. Upon arrival, Paul drinks the Water of Life and falls into a coma. This angers Chani, but she is compelled by Jessica to mix her tears with the liquid, which awakens him. Paul now has a clearer vision of the past, present, and future. He sees an adult Alia on a water-filled Arrakis and learns that Jessica is the Baron's daughter. He also sees a singular path to victory among all possible futures.The southern Fremen leaders urge Paul to challenge Stilgar to a death duel for leadership. He refuses, instead galvanizing the fundamentalists by showing that he can read their innermost thoughts. He declares himself the Lisan al Gaib and sends a challenge to Shaddam, who arrives on Arrakis with Irulan, Mohiam, and his Sardaukar troops. As Shaddam chastises the Harkonnens, the Fremen launch an offensive using atomics and sand-worms to overpower the Sardaukar forces. Paul murders the Baron and captures Shaddam and his entourage. Gurney intercepts and kills a fleeing Rabban.Paul challenges Shaddam for the throne and, to Chani's dismay, demands Irulan's hand in marriage. Shaddam admits his involvement in the destruction of House Atreides. Previously summoned by the Baron, the Great Houses arrive in orbit. Paul threatens to destroy the spice fields with atomics if they intervene. Feyd-Rautha volunteers to be Shaddam's champion, but Paul kills him in a knife duel. Irulan agrees to Paul's request for marriage on the condition that her father lives. Shaddam kneels and kisses Paul's signet ring, thus surrendering.After the Great Houses reject Paul's ascendancy, he orders the Fremen to attack the orbiting fleet. As Stilgar leads the Fremen onto the captured Sardaukar ships, Jessica and Alia reflect on the beginning of Muad'Dib's holy war.Chani refuses to bow to Paul and departs alone on a sand-worm.