Told almost entirely from the point of view of a 14-year-old Bolivian silver miner who supports his family by toiling deep under the mountains of Cerro Rico, Kief Davidson's riveting documentary is a deeply troubling look at child labor under horrendous conditions. Basilio, whose father died when he was only 2, isn't even the youngest child to work the Cerro Rico silver mines, which are nearly depleted of mineral resources after centuries of drilling; Basilio's 12-year-brother, Bernardino, works alongside him in the hopes that together they'll bring home enough money to feed their widowed mother and younger sister. The family lives in an unheated stone hut on the mountain, not far from the mine entrances; the boys' mother makes a pittance guarding the tools and belongings of the workers who return home each night to nearby Potosi, but it's hardly enough. She has no choice but to send her sons deep into the earth to a place so far removed from God that these Catholic miners feel compelled to pray to the devil for their safety. Each of the 500-odd mines that snake deep under Cerro Rico is home to a blank-eyed "Tio," a demonic idol that could be as old as the mine itself and to which wary miners offer alcohol, cigarettes and handfuls of coca leaves — a stimulant the miners chew to kill their hunger and keep them awake for shifts that can last 24 hours. In return they pray to Tio to protect them from the explosions and falling rocks that have killed countless miners over the years earning the region the ominous nickname "the mountain that eats men." Nothing is certain in this infernal region so far from the light of day, except early death: Few miners live past the age of 40, when the dust they've inhaled for years finally causes their lungs to explode. Ironically, Basilio's dream of one day escaping this terrible fate by staying in school — where, like other child miners, he's ostracized by other children, who call him "rock thief" and "dust sucker" — only drives him deeper underground: In order to afford the required school uniform for himself and his siblings, Basilio takes a job at one of the oldest and most dangerous mines. The terrifying thought of a workplace so hellish that workers actually pray to the devil for their well-being is horrifying enough, but it's doubly so when the workers are mere children. Basilio narrates his tale with such wit and wisdom that one comes away from the film wondering how much youthful potential is slowly being choked to death deep within the bowels of the earth.