The head of the US National Security Agency is assassinated in a spectacular set piece killing at Heathrow ...An airport employee and his family are found murdered in their council house in Uxbridge ...In New York, a fashionable Upper East Side osteopath receives two postcards showing the Empire State Building ...A group of migrant workers are brutally gunned down in Macedonia ...The quest to find the link between these apparently random events is pursued by Robert Harland - drawn back to a world he thought he'd left behind with a dual role for the UN and MI6.