Reuben Maitland has lost everything, his job, his marriage, his reputation. Fired from CID's elite forensic investigation unit, he is forced to turn to the other side of the law to find work.

Michael Brawn is currently enjoying the hospitality of Her Majesty at Pentonville maximum security prison. He is not who he claims to be. He has been placed there on forged genetic evidence. Evidence that was submitted to the court on Reuben's authority. But who is he, and why is he there?

Reuben is offered one chance to clear his name. He needs to discover Brawn's real identity and, more importantly, his reason for falsely entering prison. And there is only one way of getting to him. Reuben is going to have to enter Pentonville. But as he is about to find out, prison is a very dangerous place for an ex-copper.