Phil Mason, former intelligence officer and one-time instructor at the British Army School of Sniping, is struggling to make ends meet as a private investigator when he's contacted by his former MI5 liaison officer. The overstretched security service needs all the help it can get hunting down members of al-Qaeda terror cells in the UK—and Mason needs the cash. But in the murky intelligence world of smoke and mirrors, nothing is what it seems. As a routine surveillance operation escalates into a full-blown international crisis, Mason must come to terms with the unthinkable: there must be a traitor within Britain's security forces. Entering a desperate race against time to identify and avert a major terrorist threat, Mason must hastily rehone his counter-sniper skills as he returns to the business he swore he had left behind forever—the killing game.