Fifteen-year-old Cat has unwittingly entered a dangerous world. The Arcanum. There, an ancient and deadly card game is played out in familiar, and unfamiliar, surroundings. As the influence of the Game Masters, the mysterious quartet of figures who control the destiny of the players, casts its shadow over Cat's life, and as her travels inside the worlds of the Arcanum reveal tantalising glimpses of her family's past, she finds her initial reluctance to engage in the dangerous complexities of the Game is waning.