Chain of Iron

"Cordelia Carstairs seems to have everything. She's engaged to marry James Herondale, the boy she has always loved; she has a new life in London with her best friend, Lucie; and she bears the sword Cortana, a legendary hero's blade. But the truth is far grimmer. Cordelia's marriage is a lie, arranged to save her reputation. Cortana burns when she touches it. And a murderer has begun targeting the Shadowhunters of London. Now Cordelia, James, and LUcie must follow the trail of the killer. All the while, each is keeping a shocking secret: Lucie, that she is attempting to raise the dead; Cordelia, that she has sworn an oath of loyalty to a mysterious power; and James, that he himself may be the killer they seek"--Back cover.

Cassandra Clare