Forced to live on Middle Island with just her parents for company, Caitlin is lonely. The closest she's got to a friend is the grumpy fisherman, Frank, who takes her to school each day in his boat. But everything changes when Catlin finds a wriggling prawn on the beach and decides to keep it as a pet. Only it's not a prawn. It's soon the size and shape of a frog. By the next day it's the size and shape of a person and it keeps growing. And growing. What is it? Caitlin doesn't care – he's the friend she's always wanted.