Will Harper, pensioned off by the NYPD Bomb Squad, goes back to work when a letter bomb kills Jimmy Fahey, his former partner, and the celebrity author Fahey is working for. Connecting the bombing to a series of seemingly unrelated incidents involving other celebrities, Harper hooks up with a former FBI profiler named Alderman who helps him home in on a suspect. With uncooperative officials always a step behind their every move and the killer always a terrifying step ahead, the countdown begins on the planned assassination of the killer's next victim: a visiting British princess. The pair must stop the maniacal predator before he blows one of the world's most famous women sky high.