Together with her parabatai Julian Blackthorn, Emma Carstairs must learn to trust her head and her heart as she investigates a demonic plot that stretches across Los Angeles. Meanwhile, the faeries, desperate to find out who is murdering their kind, return Julian's brother Mark in exchange for the Shadowhunters' help.

It's been five years since the events of City of Heavenly Fire that brought the Shadowhunters to the brink of oblivion. Emma Carstairs is no longer a child in mourning, but a young woman bent on discovering what killed her parents and avenging her losses. Together with her parabatai Julian Blackthorn, Emma must learn to trust her head and her heart as she investigates a demonic plot that stretches across Los Angeles, from the Sunset Strip to the enchanted sea that pounds the beaches of Santa Monica. If only her heart didn't lead her in treacherous directions.