Shadowhunters Emma Carstairs and Julian Blackthorn are travelling the globe when the Clave orders them to clean up Blackthorn Hall, a crumbling Gothic mansion hidden away in Chiswick, London-or else the Clave will demolish it once and for all.

Amidst the clutter and disrepair, Emma and Julian discover secrets Blackthorn Hall has kept buried for years. Something (or someone…) else haunts the Blackthorn family's cursed home. With the help of their friends and family, Emma and Julian must restore the hall to its former glory and solve the mystery of the spectral presence which threatens any who interfere, while entertaining Shadowhunter visitors from both sides of the Atlantic.