When an awkward, heavily bullied schoolboy from a dysfunctional home discovers a beautiful water nymph hiding in an abandoned Edwardian bathhouse, he must confront his own personal demons in order to save them both from the depraved custodian who keeps the enchanted waters alive with the ritual sacrifice of children.

Katie is an isolated ten-year-old constantly looking for attention from her family. Her equally overlooked Granny, who has Alzheimers, lives with them. Though Granny's condition is at times frustrating, Katie uses it to get extra pocket money and sherry out of her, Granny is the only person who treats her like an adult. But an unexpected friendship begins to develop between them as they become close allies.