Six opposing factions run the city, each with their own particular powers, peace is held only by fragile accords, and the magic-wielding sorcerers have problems in their own faction that threaten to tear them apart.

In a London not like our own, as granddaughter of the High Sorcerer, Cassia Sims should be a powerful magician, but she's never been able to make her magic work properly, and is therefore denied entry to The Society of Young Gifted Sorcerers.

Desperate to prove herself, she's drawn into a plot by her brother, Ollivan, to make himself head of the society, and on the way she finds a trap he set for his enemies: a cursed doll that absorbs any magic that is thrown at it.

The doll escapes, rampaging through the streets of London, and Cassia must learn to work with her magic and her brother to prevent the destruction of the city.