Reuben Maitland was head of a London Metropolitan Police Special Forensic investigation unit when he was fired for breaching the rules as a result of his suspicions regarding his wife's lover. His wife had left him and his world was in ruins. He was forced to use his scientific skills of DNA testing not to discover criminals but to help them evade justice. But because of his enormous technical knowledge he still helps his former colleagues out.

He discovers that there's a convict serving a sentence in Pentonville Prison whom he suspects is in under an alias. The only way he can verify conclusively the identity of the inmate in Pentonville, is with a sample of his DNA, but to get it he needs to be sent to the Prison as a convict. He arranges this with the help of a former Met Police colleague.

Before he became a forensic scientist he was a serving policeman himself, but being an ex-copper is not something to advertise in a prison, but unfortunately the other convicts discover Reuben's guilty secret which makes his temporary detention incredibly dangerous indeed.

This story, which is only the author's second was absolutely unputdownable. It was very tense and violent and I was kept on a knife-edge almost to the last page. The author is a scientist but the many forensic science details which he introduces are explained in very non technical language and it was very clear. It was a long book, but such a page turner I shot through it in no time at all. I enjoyed this book enormously and I hope to read all his future ones as they appear.