Julie, a young doctor, is running late. She is about to pick up her daughter from school close to the City of London when there is an explosion. Sirens shriek. A police van tells everyone to take cover from radiation. She huddles in a shop with strangers - City workers, an Asian girl, an American, a Russian beauty therapist and a mysterious Chechen. Were any of them involved in the attack? Is she contaminated - and will the radiation spread to the school? As she helps the victims she is terrified about her daughter. As a second strike looms, fear engulfs the nation. Will what Julie learnt that day help MI5 prevent another attack?