Pixie's life has fallen apart: her beloved parents are swept out to sea in a fierce storm, never to be seen again, and she's sent to live with her mysterious grandma, Nanny Monkton, in a village on the edge of nowhere. On her train journey there, she meets an orphan boy called Wyld, who steals her mother's precious coin necklace. When they arrive at Nanny Monkton's, Pixie realises that she's no ordinary grandma: she lives in a treehouse and wears an eye patch, just like a pirate! As Pixie settles into life in Wendbury and befriends Wyld, she begins to uncover amazing things about her own mother, about Wyld, and the wishing well in Nanny Monkton's garden - a mystery of mermaids and magical coins. It sends the new friends on a whimsical journey to search for answers, but in Pixie's heart she knows she wants an answer to the biggest question of all: is there a wish powerful enough to bring her parents back?