In 1925, Colonel Percy Fawcett walks into the Brazilian jungle with his son Jack and Jack's friend Raleigh Rimmell, searching for a lost city he calls Z, and none of the three men are seen again. Explorer Niall McCann leads a present-day investigation into what actually happened, working from the physical evidence that has surfaced over the decades: a signet ring recovered sixty years after the disappearance, and a map marked with a code that only Fawcett's wife could read. The film examines Fawcett's own convictions, including his belief that Jack was a "chosen one" destined to find the city, and traces how that certainty may have shaped the expedition's fatal decisions. New archaeological fieldwork runs alongside the historical mystery, with digs uncovering traces of large, organized settlements buried under jungle long assumed to have been empty wilderness. Those findings force a reassessment of what Fawcett was actually chasing, and whether the Amazon he searched was ever as untouched as explorers of his era believed.