"The English have a great hunger for desolate places." That's a line from Lawrence of Arabia, and it describes the obsessive Anglo explorer/adventurer -- well-known to movies -- whose fearlessness feels at times like a death wish.

You meet another one in James Gray's The Lost City of Z, which delves into the life of English explorer Percy Fawcett (Charlie Hunnam) -- in the early 1900s, an ambitious and frustrated British Army officer with a go-nowhere posting and a dead-end career.

He gets a break when the Royal Geographical Society appoints him to lead an expedition to South America. He leads a survey team (including Robert Pattinson) into the Amazon rain forest, and it's a politically charged mission. Fawcett will be drawing borders in a way that will have crucial implications for national and colonial interests (war is looming, rubber plantations are in the balance).

For Fawcett, though, the mission is personal, and for a time, this wins the viewers' sympathy. If he succeeds, he redeems his tarnished family name and provides for his wife and growing family. Sienna Miller is Mrs. Fawcett, and again, as in American Sniper, she plays a woman who watches her husband travel the world on repeated missions, returning each time with a little less of his original self.

Fawcett falls in love with the jungle, and so does director Gray, known mostly for his urban dramas. He does some impressive widescreen location work here, and conjures some memorable images: Fawcett and crew arriving at a rubber plantation in middle of nowhere, where somehow a touring opera company is performing.

As the men move upriver, past the skeletal wrecks of previous expeditions, Gray continues to push the story with images, sometimes to a fault. The size of the initial expedition, the men involved -- these things are poorly defined. There is an Indian attack in the middle of a trackless wilderness -- so why is that horse wandering contentedly on the far bank?

Gray is actively uninterested in these details, as if urging us to think about bigger things, principally the riddle of Fawcett's metamorphosis. The rain forest changes him -- he gradually forgets that these missions are to advance his rank in England and becomes obsessed with proving his theory that an ancient and impressive civilization once existed there, a challenge to the Eurocentric world anthropological order.

Parallel discoveries beat him to the punch, but he loses none of his zeal. So there's something more to his drive to explore, but what? I think the movie asks too much of Hunnam, who is stalwart and soldierly, but doesn't suggest the complexities that Gray is after.

When he drags his eldest son along on his final, fateful mission, it suggests a complex mania (I was reminded of Harrison Ford in The Mosquito Coast) that the movie can't define and Hunnam can't project.

He remains opaque, and it wears us out. Fawcett made several trips to South America. The movie recounts most of them. After a time, we heartily second the entreaties of Mrs. Fawcett: Please, Percy, don't go back.