The head of the US National Security Agency is assassinated at Heathrow. A family are found murdered in their home, a group of immigrant workers are brutally gunned down and in New York an osteopath receives two postcards of the Empire State Building which convince him a friend is in terrible danger. The quest to find the link between these apparently random events is pursued by Robert Harland, with the help of Isis Herrick, a young female officer of M16, as Harland is catapulted back to a life he hoped he had left behind.