The epic true story of an ambitious explorer came from a New Yorker magazine article that became a book written by David Grann. James Gray wrote the screenplay and directed the film that tells the story of Percy Fawcett (Charlie Hunnam). Percy is introduced languishing with a bad legacy of his father and an unrecognized military rank of Major though he shows exception at hunting shooting a large deer in Cork, Ireland. He is transferred to the Royal Geographical Society and given an opportunity to redeem his father's troubled legacy by traveling to the Amazon.
His wife Nina (Sienna Miller) is not happy about his extended absence but agrees to raise their two sons without him. On his first trip out, he is accompanied by Henry Costin (Robert Pattinson) and commissioned to map the river to help prevent conflict between Brazil and Bogota. He witnesses the slave trade of the natives and the disrespect societies have for these isolated civilizations. The trip up the river is deadly for many of his crew but Fawcett and Costin make it to the source with the help of a native who escapes. Percy finds pottery and becomes convinced there is a lost city, which he names Zed.
Percy returns to England with his discovery and impresses an explorer of the Arctic James Murray (Angus Macfadyen). He decides to return with Costin, another explorer from his first trip Arthur Manley (Edward Ashley), and Murray. Percy engages with the natives and their culture, impressed by their agriculture. Murray is upset and becomes ill, stealing their food, and forcing them to turn back. Murray is sent off on his own and Percy believes he is dead but when they return to England, Murray accuses them of desertion. Upset, Percy abandons the Royal Geographical Society and is drafted to fight in World War I. He teams up with Costin and Manley but is hit with chlorine gas and blinded.
His grown son Jack (Tom Holland) becomes enthralled with Amazon as well and encourages his father to take one more trip. Nina has reservations but lets her son and husband venture out with support from newspapers and the forgiveness of the Royal Geographical Society. Percy and Jack set out with high hopes but encounter warring tribes and find themselves captured. The true story does not know what happens to Percy Fawcett so they hint that he was drugged by the tribe and possibly still lived with them.
The film is pretty slow and the adventures stress more the difficulty of keeping rations and communicating with the natives. The story is certainly interesting and worth a watch to learn about this ambitious explorer. Hunnam doesn't deliver the most impressive performance but seems to be improving since his motorcycle drama days. The film had potential to be really entertaining as the life of Fawcett contains a lot of action but the movie comes up short on any action.