If the Heart of Oak is real, fairies shouldn't go looking for it... Seven years ago, Rowan's mother left their London home and never returned. Now, Rowan is struggling to keep the family together. On the anniversary of her mum's disappearance, Rowan goes to the last spot she saw her. She sits beneath the same tree in the same park, and cries herself to sleep. But when she wakes, Rowan isn't the same at all... She is about to discover hidden realms, fearsome enemies and new friends. With their help, Rowan is determined to find the person she misses more than anyone. But how will they ever get home?