A sniper is killing mail carriers in Boston, Massachusetts. With a murder in a different part of the city each morning, there is no apparent motive and no clues. Some of the killings are simple executions, others are more involved and pose seemingly unnecessary risks for the sniper. With no connection between the victims other than their uniform, it seems someone hates the postal service. And that means a lot of suspects. As panic grows, US Postal Inspectors Cob and Warburton are faced with their biggest case yet. Although they are polar opposites in character - female inspector ‘Cob’ O’Cobhthaigh is hot-headed, foul-mouthed, fourth generation Boston Irish, whilst Colin Warburton is a rich, Harvard-educated WASP who’s uptight and by-the-book - they share the same dedication to their jobs and revel in their disparaging banter. As inspectors for the United States Postal Inspection Service - the oldest federal law enforcement agency in America - they have the same powers as the FBI, but only investigate crimes committed against US Postal Service personnel, property and the mail. Unless Cob and Warburton can discover how and why the killer or killers selects his targets, more innocent postal workers will die, and all mail deliveries in the city and beyond will stop until he is caught.