When someone tries to sabotage training for St Jerome's star swimmer, Harriet 'The Fish' Thompson, by putting purple die in the swimming pool, fully qualified young private detective Fletcher Moon is determined to find the culprit. His profound fear of water, however, threatens to jeopardise this water-based investigation. Much to ace reporter Mia's amusement and Moon's embarrassment it looks like he may fail to conquer his fear. Meanwhile headmistress Quinn apprehends Harriet's fellow swimmer Shell and Moon's crime busting partner Red, ignoring the protests of innocence. But why are The Pinks so keen that the swimming trial be cancelled?