It's early morning, the eve of Christmas Eve, and all of heaven is preparing for the grand celebration of Jesus' birthday. The Virgin Mary (Klára Issová) and Saint Veronica (Veronika Žilková) are baking mountains of sweets, the Three Kings are preparing a cake and the choir of angels are rehearsing carols. Only one angel seems to be there in addition and seems to be just getting in everyone's way - Petronel (Ivan Trojan), a stubborn klutz and overachiever.
What he touches, he spoils, but he never admits his mistake. Soon, he's pitting all the saints against each other. The only one who still has patience with Petronel is the Lord God himself (Jiří Bartoška), but even he is eventually offended by Petronel. As a punishment, he is sent to the earthly world to reform a single sinner, otherwise he will end up as a fallen angel in hell on Christmas Eve. Terrified, Petronel, transformed into a beggar, goes among mortals of whose lives he has no idea.
His guide is the mischievous devil Uriáš (Jiří Dvořák), who has a great time at Petronel's expense. Petronel wanders through the snowy countryside, trying to find a sinner to reform. But he hasn't the slightest idea of people's wishes, desires, worries and loves...