The fire at a boarded-up Catholic church raged hot and fast, lighting up Boston's South End and killing 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. Boston firefighter Jack McGee, who lost his best friend in the blaze, suspects arson, and is convinced department investigators aren't sufficiently connected to the city's lowlifes to get a handle on who's behind the blaze. McGee takes the case to Spenser, who learns that the fire might be linked to a rash of new arsons, and he follows the trail of fires to Boston's underworld. Spenser has to find the firebug before he kills again -- and stay alive himself.