As the novel begins, 15-year-old Paul Atreides prepares to leave his home on Caladan and move to the desert planet Arrakis, which his father has been appointed to rule by the emperor. Soon after arriving on Arrakis, Paul's father is betrayed by Paul's teacher, Dr. Yueh, and killed. Paul becomes duke, but he is a duke in exile—Harkonnens now rule Arrakis while Paul escapes to find sanctuary with the desert Fremen people. Over time, Paul gains acceptance and respect in the Fremen community, taking the names Usul and Muad'Dib according to Fremen custom. For two years he lives with the Fremen and gains authority among them, finally becoming their leader. Using strict military discipline and the religious passion of the Fremen, Paul shapes the Fremen into an army able to conquer even the emperor's forces. When he unleashes this army on the emperor's army, he gains victory and eventually becomes emperor. Paul is also the Bene Gesserit's Kwisatz Haderach—the man genetically able to access ancestral memories through both male and female avenues. He can look within and see the dark place that the women of the Bene Gesserit cannot see. Through a diet high in spice, he is also able to see into the future with its ever-changing possible paths. This allows Paul to make decisions that make certain futures more likely.
The Lady Jessica is a member of the Bene Gesserit, an organization of women whose goal is to control procreation in order to breed offspring with specific traits. Ultimately, they desire to breed the Kwisatz Haderach, a male with the ability to see into time and space and access ancestral memories through both the male and female lines. Jessica's own genetic heritage is unknown at the beginning of the novel, though it is known she was supposed to bear a daughter, not a son, to further the Bene Gesserit genetic breeding program. However, later in the novel it is revealed she is the daughter of Baron Harkonnen, making Paul the grandson of Baron Harkonnen. Jessica is able to win the trust of the Fremen by fulfilling a prophecy among them. This prophecy stated a Bene Gesserit woman would come among them. Her son would be the Lisan al-Gaib, a messiah who would lead them to freedom. The prophecy is one planted by the Bene Gesserit Missionaria Protectiva in case of just such a need. She becomes the Reverend Mother of the Fremen when she drinks the poison spice drug and changes it into the harmless, euphoric drug the Fremen use for religious celebrations.
Baron Vladimir Harkonnen
Baron Vladimir Harkonnen is the ruler of House Harkonnen, the enemy of House Atreides, and the orchestrator of Duke Leto Atreides's betrayal and death. His "plans within plans within plans" include conspiring with the emperor to overthrow Duke Leto's rule of Arrakis and recruiting the duke's servant Dr. Yueh through the capture and torture of Yueh's wife. The baron often controls people by leveraging their weaknesses against them. He helps them indulge their addictions to make them dependent on him. He exploits their emotions—from love to revenge—to coerce them into doing his will. When these methods do not work, he's quick to kill—or order others to kill, so he can keep his hands clean. Although the baron is successful in overthrowing the Atreides' rule of Arrakis, ultimately he is killed by Alia Atreides, Paul's younger sister.
Duke Leto Atreides
The downfall of Duke Leto Atreides is already planned and in motion before the novel begins. That he is doomed—a fact acknowledged by the Reverend Mother Gaius Helen Mohiam at the beginning of the novel—shapes his portrayal as a character. His love for his concubine Jessica, his devotion as a father, and his compassionate treatment of his men and those he rules are evident, yet he is calculating enough to make deals with smugglers behind the emperor's back and to pretend he suspects Jessica when he believes the Harkonnens are trying to frame her. For all of his strategies and noble qualities, however, the duke is caught in the trap set by Baron Harkonnen. The duke is betrayed by the trusted Dr. Yueh. His final act is to kill the baron's inner circle of advisers and servants using a poison gas concealed inside a false tooth.
Thufir Hawat is a Mentat, a man trained to calculate at a level far beyond the normal human capacity. Mentats function as human computers in an age where machine computers are no longer used. An older man who served House Atreides through three dukes, Hawat is nevertheless corrupted by Baron Harkonnen, who convinces him Lady Jessica is the duke's betrayer. Before he dies, however, he learns of his error and is forgiven by Paul Atreides.