Temple leads an investigation to catch a serial killer who is murdering prostitutes, but after viewing the women's mutilated bodies he doesn't know if he's strong enough to see the job through; Mannion comes under pressure to hire a politically correct candidate for a district-commander post.

Mannion decides to declare war against street gangs after a drive by shooting kills an innocent pedestrian. Two Latino gangs (the ""Colombian Guardian Crew"" - C.G.C. - and ""Los Muertos"") - one Cuban and one Salvadorian - are in war with each other over territory limits and Mannion sends his best men to catch the main leader accused of killing the pedestrian: Carlos ""El Gato"" Cesar, one of the most dangerous gang members in the city. Meanwhile, Mannion has suspicions that the same man that reported a criminal fire is the one who started it; and Nick has to face his fears after being badly beaten up by a robber.

When two children are shot by a 7-year-old boy, Mannion makes it his mission to find exactly how the boy got his hands on a gun.

When Mannion questions the 7-year-old, he learns that the youngster took the gun from his 15-year-old brother who reveals that he got the gun from a ""guy on the street"" near his school. With the help of Temple and Debreno, Mannion sets up a sting and discovers that the weapon was actually a gun that the police had confiscated in a ""buy-back"" program. Now, with the Public Safety Commission breathing down Mannion's neck, he must track down the culprits before any more guns hit the street or any more children get hurt.

Ricky and a friend collapse at Ricky's birthday party and are taken to the hospital, where they are diagnosed with MDMA ingestion (a.k.a. ecstasy). Mannion and his men hit the streets trying to reach the source of the drug distribution network, which leads them all the way to a man in the Netherlands. Meanwhile, Clive and Ella's sister fight over Ricky's custody, and Ricky chooses to go with his aunt to Florida. Debreno and Temple's friendship is shaken and Temple punches Debreno, still about the Lester Richards case. Brander and Cutter track down an ATM thief, a job usually done by the secret service agents – who offer Cutter a position on their staff.