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…