The fire at a boarded-up Catholic church raged hot and fast, lighting up Boston’s South End and killed three firefighters who were trapped in the inferno. A year later, as the city prepares to honor their sacrifice, there are still no answers about how the deadly fire started. Most at the department believe it was just a terrible accident - faulty wiring in a century-old building. But Boston firefighter Jack McGee, who lost his best friend in the blaze, suspects arson. McGee is convinced department investigators aren’t sufficiently connected to the city’s lowlife to get a handle on who's behind the blaze. So he takes the case to Spenser. Our hero quickly learns not only that McGee might be right, but that the fire might be linked to a rash of new arsons spreading through the city. Spenser follows the trail of fires to Boston’s underworld, bringing him, his trusted ally Hawk, and his apprentice Sixkill, toe-to-toe with a dangerous new enemy who wants Spenser dead and doesn’t play by the old rules. The challenge? Spenser needs to find the firebug before he kills again – and stay alive himself.