"Clockwork Princess" is the third book in the Infernal Devices series by Cassandra Clare. Set in Victorian London, it follows the story of Tessa Gray, a young woman with the ability to shapeshift. Tessa is caught in a love triangle between two Shadowhunters, Will Herondale and Jem Carstairs, as they face the threat of the evil Mortmain and his army of automatons. The novel explores themes of love, sacrifice, and the struggle between good and evil. As the characters confront their destinies, they must navigate complex relationships and the challenges of their world, ultimately leading to a climactic battle that will determine their fates.