Agent 21: Codebreaker

Secret agent Zac Darke is back for his third mission - and the stakes have never been higher.

An unknown bomber is conducting a terror campaign in London. After an explosion on the tube leaves someone dead, Zac and his team are brought in to try and work out how this terror cell operates - but clues are scarce and they have no idea where, or when, the bomber will strike next. A teenage boy, currently detained in a young offender's institute, claims he has the answer - but before Zac can question him, the boy is shot and falls into a coma. Will Zac be able to break the cipher before the bomber strikes again?

• "Nobody takes you to the action better than Ryan, because he is the real deal." --Evening Telegraph

Chris Ryan served in the SAS for 10 years and was awarded the Military Medal for his work under cover in Iraq. He now travels the world as a security expert, putting all his real-life experience into his books and TV shows. You can find out more about him at www.chrisryanadventures.co.uk.