Daniel Radcliffe plays real-life adventurer Yossi Ghinsberg, an Israeli backpacker who survived a terrifying ordeal in the Bolivian jungle in 1981.
His plight really is the stuff of nightmares.
Trekking around South America after national service, Yossi and two friends he has made along the way find themselves talked into undertaking an expedition in search of a lost Indian village by a blustering Austrian stranger (Thomas Kretschmann).
Unsurprisingly, the venture goes awry and Yossi ends up stranded alone, without supplies, in the jungle.
Director Greg McLean, creator of Australian horror thriller Wolf Creek, makes us squirm and flinch as Yossi undergoes a string of gruesome perils, including rapids, bogs, fire ants, snakes, a jaguar and, most gruesome of all, a wriggling parasitic worm.
Some hallucinogenic episodes and fantasy sequences don’t really work, but Radcliffe’s wild-eyed grit keeps us glued.