When Sheikh Umar declares a perpetual war against the West, London is plunged into the front line with a deadly jihadi assault on Downing Street. Josh East a new recruit to MI5's elite Orion unit lends decisive support and when the trail leads to Batley in West Yorkshire he teams up with MI5's Lucy Hall to track and eliminate the terrorist cell. Events move at a fast pace when East and Hall uncover a much greater threat to Great Britain. Sheikh Umar is plotting to turn London into a radioactive wasteland by hijacking and diverting a trainload of high-level nuclear waste into central London. East and Hall make a formidable team as they launch a counter-attack to prevent a new Chernobyl arising in the heart of London.