Out to catch crabs in her small dory and surrounded by fog, Clementine Nesbitt spies two boats dangerously close to one another. Confusing shouts and the sound of something heavy splashing into the water startle her and, although the boats seem to have missed each other, it sounds as if something went over board. Edging closer, Clem spots a mysterious brown shape in the water. Deeply curious to solve the mystery ensuing from this incident, Clem is forced to ask many questions – even of those people she thought she could trust most.