A serial killer is wreaking havoc in Roarhaven and its surroundings. At first glance, the victims have nothing in common except for the very imaginative and intricately detailed manner of their deaths. Skulduggery and Valkyrie are in the dark, but then they receive a coded message from the perpetrator. The murderer calls himself "Replacement" and seems to want to test the detectives. With Skulduggery's impressive deductive skills, they try to solve his riddle and find him before more innocents die. But what is his motive, and what is really behind it all? Meanwhile, Valkyrie's little sister is busy trying to save the world.

Horror master Derek Landy brings back beloved and long-missed characters, allowing his tried-and-true detective duo, Pleasant and Unrest, to embark on new thrilling adventures filled with action. The witty dialogues are, as always, expertly delivered by voice artist Rainer Strecker.