Fidibus is the son of two notorious sea devils, but he doesn't want to learn any devilish tricks. He wants to be good, no matter what his parents say. After Fidibus performs too many good deeds, he is punished by being locked in an empty shell. This news spreads among the sea creatures. And so, his friends bravely rush to his aid. Loving ink drawings by the popular illustrator Werner Klemke depict how they do it.