The term Code Zero was coined in the first Joe Ledger book, Patient Zero, to indicate a threat composed of the Seif-al-Din virus, which if released would inflict a zombie plague upon the world. This book is pretty much a sequel to that first book with a smattering of threats from the other books thrown in for good measure. Over the course of the first five books of the series Joe Ledger and the DMS have turned aside one threat after another (designer plagues, pathogens, engineered viruses, etc) and they have been locking away samples of these threats in their most secure facility. Very few people even know these things exist and all of these secrets are closely guarded for good reason. However, this time around the threat comes from within the DMS itself and that makes it hard for Joe Ledger and Echo team to get the job done as they are unaware they have been betrayed...

A series of terror attacks start to occur around the world and it is obvious they are all related, with someone named Mother Night taking responsibility. Mother Night appears to support an anarchist agenda but a couple of things just don't add up. First, the attacks don't seem designed to cause global anarchy and second, they are composed of various threats that the DMS has already faced and contained. Threats that would be impossible for anyone to duplicate in such a short period of time, so how did Mother Night get her hands on them?

This book jumps back and forth between the present day, where Joe and Echo team are in the field trying to contain the various attacks, and flashbacks into the past, where the origin of Mother Night is detailed out. Due to certain events in their own past the DMS has a real blind spot when it comes to figuring this one out and many innocent people pay the price. Long time nemesis, Vice President Collins, is back in the center of the storm again and it all builds up to a showdown at DragonCon where pop culture based humor takes center stage.

Code Zero is another solid entry in the Joe Ledger series but it is paced a bit slower then the prior books. Ray Porter is back at the mic doing the narration for the audiobook and his performance is excellent as always.