When the tides roll in, death follows. That is what eighteen-year-old Hania has been told all her life. For the depths of the sea hide the cruel and magical tidespeople, strange gods and creatures of the water who see human life as nothing more than a game. When they sweep her brother away with them, a new pet for their queen, she knows she has no option but to get him back. And her one hope is Aven, a lonely, imprisoned selkie desperate to return home. So she strikes a deal. She will return his skin, and his power with it, and in exchange Aven will take her to the Realm of Tides. But once there Hania finds a world unlike any she imagined. A world of beauty and danger, of magic beyond any the old tales could have prepared her for. The longer she finds herself there the more fear of the undersea realm turns to awe-and an uneasy alliance with Aven turns to something far more thrilling and far more damning. But here deadlier creatures than Aven lurk, eager to kill her, claim her, or break her. Her brother's capture is only the beginning of the game. A game of hearts and lives, loyalty and cunning. And to save them all she must be willing to play it and win-or die trying.