Percy Fawcett embarks on multiple expeditions to the Amazon in search of the mythical city he names “Z.” During his final expedition in 1925, Percy, along with his son Jack Fawcett (played by Tom Holland), disappears without a trace. The film suggests that they might have found the lost city or encountered some other peril in the jungle.
Nina Fawcett (played by Sienna Miller), Percy’s wife, spends years holding onto hope and advocating for her husband’s legacy, despite societal norms that frowned upon a woman pursuing such interests. Eventually, Percy’s exploration becomes something of an obsession for his family as well.
The film shifts to World War II, where Percy’s eldest son, Jack, is now a soldier. During the war, Jack visits James Murray (played by Angus Macfadyen), a former colleague of Percy’s, to learn more about his father’s disappearance. Murray provides Jack with some information about a hidden city deep in the Amazon, reinforcing the possibility that Percy did find the lost city.
The movie then returns to Percy in the Amazon. It suggests that, after years spent among indigenous tribes, Percy and Jack chose to stay in the jungle, adopting the local way of life. The film intentionally leaves the fate of Percy and Jack ambiguous, allowing for interpretation and speculation about whether they found the lost city or succumbed to the challenges of the rainforest.
The closing scenes depict Nina attending an event where she learns that other explorers claim to have discovered evidence of a sophisticated ancient civilization in the Amazon. The implication is that Percy was right in his theories about advanced civilizations existing in the jungle.
The film concludes with Nina choosing to explore the Amazon herself, seeking answers about her husband and son’s fate. It ends on a note of mystery and adventure, leaving the audience to ponder the ultimate destiny of Percy and Jack Fawcett in the uncharted depths of the Amazon rainforest.