Herman the Clown sets out to find his father, whom he hasn't seen since he set off to measure the Earth with his feet. He is secretly followed by the son of Max the Magician, ten-year-old Roni. And so begins an exhilarating adventure full of magic, twists and colorful circus life.

The people at Circus Hepokatti decide to throw a big surprise party for Herman The Clown, but no one seems to know when Herman's birthday is. No one has ever organized a birthday party for him before. The birthday arrangements take a surprising turn when the ruthless leader of a rival circus, the ringmaster Tilpehööri, wants Herman to be the attraction of his own circus by any means necessary. When his attempts to trick Herman fail, Tilpehööri decides to bring in the more extreme methods, and soon things start to get weirder and weirder at the Circus Hepokatti.