Lübeck is threatened! For centuries, the sinister ruler Zanrelot (Udo Kier), who is up to mischief in the underworld under the foundations of the old walls, has been trying to gain power over the Hanseatic city. From there, Zanrelot wants to destroy everything in the world that makes life worth living: colors, laughter, love. For the last few centuries, "Guardians" have prevented the evil machinations of Zanrelot. But now his last and most stubborn adversary has died, leaving behind a heavy legacy. The four children Karo, Pinkas, Otti and Leonie - nephews and nieces of the deceased - equipped with magical abilities, are supposed to save the city as new "guardians" and protect the world from the unimaginable.