Cordelia Carstairs lost everything that was meaningful to her. Her father was killed, she was unable to become Lucy's parabatai, and her marriage to James Herondale is falling apart at the seams. Now the girl is bound by an oath to the demoness Lilith and cannot wield the sword Cortana. Hoping to forget about her problems, Cordelia goes to Paris with Matthew Fairchild. But terrible news comes from home: London is threatened by the Prince of Hell, Belial. Cordelia and her friends must save their city. To do this, they will have to put aside pride and fears and learn to trust each other again. After all, if they lose, they will lose everything, even their souls.