Mauritz Grafvenhjelm, alias Moppe, an impoverished nobleman, and his friend Ville enjoy a carefree life as vagabonds in summery Porvoo until Moppe finds a large sum of money and receives a reward for it. After celebrating thoroughly at the Belvedere restaurant, he wakes up in the morning in a cell with no memory of what happened and learns that he has become engaged to the restaurant owner, Miss Svea Jonson.

The story of poor brake man Jaakko and beautiful train conductor Mimmi, who is also admired by welder Heikki, rapper Ranssu, bricklayer Martsu, and engineer Immu. The story also involves Jenny and Aleksi, a Roma couple who run a construction site canteen.