The biggest explosion since the German Blitz is about to hit London. MI6's agent in Islamic State is running for his life - his cover blown - but desperate to get his information out. While in London, the terrorists finalise their plans for a massive radioactive dirty bomb in the heart of the City. The components for the bomb are all in place, and the Metropolitan Police are doing their best, but it just isn't enough. At every turn it seems the bombers are one step ahead, killing anyone who stands in their way - police officers, bystanders even their own people. The only opponents the terrorists haven't allowed for are: an injured man who should still be in hospital, a mentally unstable jihadi bride looking for revenge, and a young MI6 analyst, who despite her skills has never seen active duty. Deep underground a desperate game of cat and mouse is being played out on the swaying rattling carriages of the London Tube. This could be a good time to be somewhere else - anywhere else.