Set in the late Yuan dynasty, the story revolves around a pair of priceless and extremely powerful weapons, the Heaven Reliant Sword (倚天劍) and Dragon Slaying Saber (屠龍刀), which are coveted by many martial artists in the jianghu. Either or both of them are thought to allow their wielder to rule the wulin (martial artists' community), according to a widely circulated mantra which goes, "Honoured by the wulin, the precious Saber slays the Dragon. It commands the world. Who dares to disobey? If the Heaven Reliant does not appear, who can challenge it?" (武林至尊，寶刀屠龍，號令天下，莫敢不從！倚天不出，誰與爭鋒？). The origins of this mantra are not known at the beginning of the story.  The protagonist, Zhang Wuji, is of mixed heritage: His father, Zhang Cuishan, is an apprentice of Zhang Sanfeng, the highly revered leader of the Wudang Sect; his mother, Yin Susu, is the daughter of Yin Tianzheng, the chief of the "unorthodox" Heavenly Eagle Cult. He spent his childhood on a reclusive northern island, where he was born, with only his parents and his godfather, Xie Xun, to keep him company. When he is about 10 years old, he returns to the Chinese mainland with his parents. They soon find themselves the target of several martial artists, who try to force them to reveal the whereabouts of Xie Xun and the Dragon Slaying Saber. His parents refuse and commit suicide. At the same time, Zhang Wuji is wounded by the Xuanming Elders, but he survives after seeking medical treatment from Hu Qingniu, an eccentric physician.  After ending up in an isolated valley by chance, Zhang Wuji discovers the long-lost Nine Yang Manual, masters the inner energy skills described in the book, and becomes a formidable martial artist. Later on, he helps to resolve the conflict between the Ming Cult and the six major orthodox sects, which are bent on destroying the cult. He earns the respect of the cult's members and becomes its leader after mastering the skill 'Heaven and Earth Great Shift'. He reforms the cult and helps to improve its relations with other sects. He becomes a key figure in leading the rebel forces to overthrow the Yuan dynasty.  Throughout his adventures, Zhang Wuji finds himself entangled in a complex web of love relationships with four maidens. The first, Yin Li, is a horribly disfigured girl who is actually his maternal cousin. The second, Xiaozhao, is a Chinese-Persian servant girl who understands him very well. The third, Zhou Zhiruo, is a childhood friend whom he develops a strong bond with. The fourth, Zhao Min, is a Mongol princess and his former arch-rival. Yin Li is apparently killed in the middle of the story while Xiaozhao returns to Persia after it is revealed that she is destined to lead the Persian Ming Cult.  Zhou Zhiruo soon falls in love with Zhang Wuji, but has to turn against him as she is bound by an oath she made in front of her teacher Miejue, who hates and distrusts Zhang Wuji and anyone related to the Ming Cult. Miejue devises a vicious scheme for Zhou Zhiruo to seize the two weapons by exploiting Zhang Wuji's love for Zhou. Zhou Zhiruo also turns vicious after Zhang Wuji reneges his promise to marry her and swears vengeance on him. Zhao Min was initially Zhang Wuji's rival as they were on opposing sides. However, Zhao Min gradually falls in love with Zhang Wuji after their various encounters, and she even turns against her clan to help him.  At the end of the novel, Zhang Wuji decides to retire from the jianghu after he mistakenly believes that the Ming Cult's members are plotting to betray him. He decides that Zhao Min is his true love and they leave to lead a reclusive life far away from society. (The second edition of the novel has an ambiguous ending about Zhang Wuji's relationship with Zhou Zhiruo.) Zhang Wuji gave up an opportunity to become a ruler because the Ming Cult eventually overthrew the Yuan dynasty. Ideally, Zhang would have become the new emperor, but instead, Zhu Yuanzhang takes the throne and founds the Ming dynasty.  In 2005, Jin Yong published a third edition of the novel, which has a slightly different ending from the earlier versions. In this edition, Zhang Wuji feels disillusioned after failing to save a general's life and addressing Han Lin'er's death. He relinquishes his leadership of the Ming Cult to Yang Xiao and Fan Yao, and then leaves the Central Plains with Zhao Min.