As people in Valleby are looking forward to Valleby Day, a thief suddenly strikes and carries out a series of thefts, leaving behind symbols linked to the zodiac and space.

Everyone in Valleby is looking forward to Valleby Day when a thief suddenly strikes and commits a series of thefts. The thief leaves behind symbols linked to the zodiac and space. The thefts seem to be aimed at ruining Vallebydagen. Lasse and Maja throw themselves into the case and engage the grumpy master thief Lillie Ragnarsson as the mastermind of the investigation, which soon develops into a cat-and-mouse game where the thief always seems to be one step ahead.—Sfanytime