Two outcasts find themselves caught in a web of forbidden love, dangerous magic, and dark secrets that could change the world forever in the start of a riveting epic fantasy series from the #1 New York Times bestselling author of The Shadowhunter Chronicles.

In the vibrant city-state of Castellane, the richest of nobles and the most debauched of criminals have one thing in common: the constant search for wealth, power, and the next hedonistic thrill.

Kel is an orphan, stolen from the life he knew to become the Sword Catcher--the body double of a royal heir, Prince Conor Aurelian. He has been raised alongside the prince, trained in every aspect of combat and statecraft. He and Conor are as close as brothers, but Kel knows that his destiny is to die for Conor. No other future is possible.

Lin Caster is one of the Ashkar, a small community whose members still possess magical abilities. By law, they must live behind walls within the city, but Lin, a physician, ventures out to tend to the sick and dying of Castellane. Despite her skills, she cannot heal her best friend without access to forbidden knowledge.

After a failed assassination attempt brings Lin and Kel together, they are drawn into the web of the mysterious Ragpicker King, the criminal ruler of Castellane's underworld. He offers them each what they want most; but as they descend into his world of intrigue and shadow, they discover a conspiracy of corruption that reaches from the darkest gutters of Castellane to the highest tower of its palaces. As long-kept secrets begin to unravel, they must ask themselves: Is knowledge worth the price of betrayal? Can forbidden love bring down a kingdom? And will their discoveries plunge their nation into war--and the world into chaos?