Valkyrie Cain, along with her mentor Skulduggery Pleasant, are back for another magical mystery. This time the fate of the whole world may rest in their hands if they can't solve the case.

It all starts when a series of sorcerers turn up dead. It does not take long for everyone to notice a pattern in the victims: they are all teleporters. Unfortunately, previous events from earlier books in the series has placed Skulduggery outside of the Sanctuary and, thus, unable to assist in the investigation. That does not prevent him and Val, as well as their other cohorts (Tanith Low, China Sorrows, and Ghastly Bespoke), from following up with an investigation of their own.

It quickly becomes clear that the Sanctuary, the governing body of the magicks that is part police/part council, has a mole that is helping the dark forces who are led by the mysterious Batu. Before long, our heroes learn that the Batu is hoping to use a teleporter to open a portal to another dimension in order to release the Faceless Ones, old evil god-like creatures who once tortured humanity centuries earlier. If these Faceless Ones are allowed to return, humanity will once again be enslaved.

Skulduggery and Val face a number of hurdles in order to stop the Batu, including fending off the official investigation, which is being led by a bumbling detective; guarding the remaining teleporter, an arrogant and untrained teen named Fletcher Renn; and avoid being captured themselves.

As with the earlier books in the series, there is a nice blend of humor, action, and mystery. Landy has created a wonderfully interesting world filled with quirky characters, interesting settings, and unique dilemmas. It is a really strong addition to the series, and it concludes with a major cliffhanger that will leave the reader wishing the fourth book was already out!