When Sheikh Umar declares a perpetual war against the West following the collapse of Islamic State London is plunged into the front line with a deadly jihadi assault on Downing Street. Josh Ryan a new member of MI5's 'Orion' elite counter terrorism team lends vital support and when the trail leads to Leeds he teams-up with MI5's Senior Intelligence Officer Lucy Hall to track and identify the terrorist cell. Events move at a fast pace as Ryan and Hall are forced to combat a much greater jihadi threat as Umar threats to turn London into a radioactive wasteland.