Something stalks the London darkness, marking its territory with brick dust and blood. Something killed Saul's father Garamond and left him to pay for this crime. But a shadow from the city tunnels brought Saul out of his prison cell and gave him freedom. Someone called the Rat King has discovered the truth about his royal inheritance - a new world beneath the streets of London. A world in which Saul will take his place in the plan of revenge against the ancient enemy of the King - the Pied Piper.