Dozens of people from Copiapó, Chile, work in the San José mine. The owner ignores the warnings of the failing stability of the mine, which collapses a short time later. The only path inside the mine is completely blocked, and the thirty-three miners manage to get to the rescue chamber. They discover that the radio is useless, the medical kit is empty, the ventilation shafts lack the required ladders, and there is very little stored food. Mario Sepúlveda becomes the leader of the miners, dividing the food in rations and stopping the outbursts of violence or despair. The mine company does not attempt any rescue, and the relatives of the miners gather around the gates.