The fourth title in the Children of the Red King quintet, THE CASTLE OF MIRRORS. Charlie and his friends are back in danger, and the balance of power between the Children of the Red King has never been more dangerous. Billy finally gets his longed-for parents, but he soon wishes he hadn't when the oaths he's forced to sign come flying through the air at him. Charlie is haunted by a ghostly horse, mad with rage over an ancient wrong that happened in the sparkling Castle of Mirrors. The castle was petrified from stone into glass by the socerer Yorath in a terrible fire. Charlie's good friend Olivia is haunted too - but no one knows her new secret. Even with the power of Tancred's storms and Lysander's ancestors, Charlie Bone is running short of allies - just when he needs them most.