When a fire breaks out in the supermarket where Bosco and his mother Rose are doing some late night shopping, Bosco rescues most of the shoppers but cannot save a young mother when she goes back inside to retrieve her purse. After Jimmy tells him that the fire was probably deliberately set, Bosco is convinced that he saw the arsonist in the crowd outside after the fire. Sgt. Cruz gets Bosco and Faith assigned to the Anti-Crime Unit for a few days so that they can track the guy down. At the scene of another supermarket fire the next night, Faith takes down license plate numbers, Cruz photographs the crowd and cars at the scene, and Bosco nabs the man he saw in the crowd the night before. The man turns out to be a fire buff, but Faith and Cruz's work bears fruit and they find their arsonist -- the son of Doug Maple, an NYFD arson investigator. A depressed Sully is still on leave, drinking too much, and sleeping on the couch at Ty's and Carlos' apartment; Doc connects with an attractive