In the early 20th century, British explorer Percy Fawcett is a dedicated soldier and a respected cartographer, though undecorated and largely unrecognized by his peers. His life takes an unexpected turn when the Royal Geographical Society offers him a chance to lead an expedition to uncharted territories in the Amazon jungle. While mapping the border between Brazil and Bolivia, he becomes consumed by the lush wilderness and enigmatic evidence of a complex civilization, which he hypothesizes is the lost city he later names "Z." Driven by his longing for historical significance and the desire to restore his family’s stained honor, Fawcett is steadfast in his belief of the city's existence, despite the skepticism of the scientific community.

Fawcett's obsession with finding the city compels him to embark on multiple perilous journeys, navigating the dangerous Amazonian landscape and confronting the numerous challenges it presents, including hostile tribes, deadly diseases, and treacherous companions. With the unwavering support of his wife, who faces her own societal battles at home, and the camaraderie of his loyal aide-de-camp, Fawcett perseveres in his quest. As each expedition brings him closer to the truth, it also takes a toll on his family life and reputation. His undying quest for Z becomes a defining piece of his identity, as the mystery of the jungle lures him back time and again.