Mostro follows the first 24 hours after the disappearance of Yuriko, a young rebellious factory working girl, by the hands of the police. Lucas must struggle with his own state of shock and a system that reveals itself as a labyrinth full of fake and dangerous exits. Desperate, he commits an act of vandalism and scapes the furious cops. Absolutely helpless, he tries to at least access the memory of her, using the same chemical drugs that she thought him to use to explore inside himself. But while the uncertainty grows, Luca's visions decay, just as the world around him.