Keller, an old sub-aquatic locomotive engineer, and his son Caelum witness a train collision and rescue from its wreckage Berenice, an orphaned pre-adolescent girl-snail. Keller and Caelum adopt Berenice as a member of their family. Keller even names his beloved steam engine after his "daughter". When Berenice reaches puberty, both Keller and Caelum fall in love with her, becoming romantic rivals. A disturbed Berenice runs away to marry a Zepplin pilot, only to be kidnapped by her adoptive father. Keller is blinded in a train mishap. Caelum loses his head and turns into a flower. Berenice turns into a cactus.