Chain of Thorns

In Cassandra Clare's Last Hours series finale, James and Cordelia have to preserve London and their marriage.

A Shadowhunters book is called Chain of Thorns.

Cordelia Carstairs has lost everything that she held dear. She had seen her father's death, the demise of her hopes to become a parabatai with Lucie, her closest friend, and the breakdown of her marriage to James Herondale in a matter of weeks. To make matters worse, she has lost her Shadowhunter abilities as she is now enslaved to Lilith, an old demon.

Cordelia flees to Paris with Matthew Fairchild in the hopes of losing herself in the vibrant nightlife of the city. However, reality sets in when startling news reaches us from home: Tatiana Blackthorn has escaped the Adamant Citadel, and Belial, the Prince of Hell, is posing a fresh danger to London.

Cordelia returns to a discontented and chaotic London. An unexpected adversary has exposed the long-kept truth that Belial is James and Lucie's grandpa, and the Herondales are now suspected of having demonic relationships. Although Cordelia has always felt that her love for James is doomed, she is divided between wanting to protect him and the prospect of starting a new life with Matthew. Nor are her friends able to assist her; torn apart by their own secrets, they seem doomed to confront this alone.

Time is of the essence, as Belial's scheme is set to overwhelm the London Shadowhunters like a terrible tidal wave, cutting off Cordelia, Lucie, and the Merry Thieves from any kind of assistance. Alone in a dark London, they have to confront Belial's lethal army. Cordelia and her friends will need to overcome their pride, find bravery, and learn to trust one another once again if they are to preserve their city and their families. They could lose everything, even their souls, if they fail.