A bewitching and powerful tale of sparkling magic, spellbinding mystery and a friendship worth risking everything for, perfect for fans of Tamzin Merchant, Abi Elphinstone and Anna James. Thomasina and Anne are looking for adventure when their friend, Henry, disappears – snatched by a mysterious creature, and dragged into the depths of the River Thames. Determined to save him, the girls venture into the deep, and discover the enchanting Free Waters: a vast, glittering underwater city, home to mermaids and sirens. But the Free Waters are threatened by an evil Sea Queen. It is she who has Henry – and the girls must complete three treacherous and impossible magical tasks if they are to save his life … An unputdownable and exciting new tale from the bestselling author of The Miraculous Sweetmakers: The Frost Fair.