Eleven year old Oscar Flowers is on a quest to make sense of the strange world of adults that surround him in the seaside town of Tidetown. The bizarre behaviour of his parents and great aunt impels him to search for the blue tiger, a powerful and beautiful animal that will save his family from themselves. Mrs April, the town’s librarian, helps Oscar in his pursuit of knowledge and generously shares her great love of books with him. A deep and wondrous friendship develops. Yet as Oscar falls under the influence of his peers, the fishmonger’s peculiar twin daughters, Perch and Carp, he becomes embroiled in a dark crime of vengeance with seemingly disastrous consequences.