Morrigan Crow is determined, daring and ready for a new challenge: to step into her destiny as a Wundersmith, master the mysterious Wretched Arts, and control the power that threatens to consume her. She and her friends are proud to be in their second year of attendance at the magical Wundrous Society, and together they can face anything. But a strange illness has taken hold of Nevermoor, turning its peaceable Wunimals into mindless, vicious unnimals on the hunt.

As victims of the Hollowpox multiply, panic spreads. And with the city she loves in a state of fear, Morrigan quickly realises it is up to her to find a cure for the Hollowpox, even if it will put her – and the rest of Nevermoor – in more danger than ever before…