Cordelia Carstairs has lost everything that matters to her. She has seen her father murdered, her plans to become parabatai with her best friend, Lucie, destroyed, and her marriage to James Herondale crumble. Even worse, she is now bound to an ancient demon, Lilith. After fleeing to Paris with Matthew Fairchild, shocking news arrives. London is threatened by the Prince of Hell, Belial. Cordelia is torn between her love for James and the possibility of a life with Matthew. But Belial's plan is like a deadly wave. To save their city -- and their families -- the Shadowhunters will have to muster their courage and trust one another again. If they fail, they may lost everything -- even their souls.