
Teenagers Alan and Ian cruise down a city street smashing mailboxes, while Harold's younger brother, Ian, is forced to videotape their antics. The two older kids' thrill-seeking escalates when they smash the window of a store and accost the cashier. When the cashier opens fire, both he and Ian fall to the ground, and the other two take off running, Harold throwing the video camera into a dumpster before being caught by police. August and Chase question Harold at headquarters, but he has been threatened by Alan not to talk, or he and his mother will be killed.
Detectives August Brooks and Chase McDonald meet when August and several officers are being overwhelmed by criminals in an explosive shootout. Chase arrives in his Porche and immediately neautralizes the situation with a grenade launcher. Moments later, August discovers that Chase is his new partner, and they are immediately assigned the case to track down a bomber - nicknamed the Daybomber - who has set off a series of explosions in his quest to warn people of the advances of technology.
Chase and August are at August's gym, where they are volunteering their time to help keep kids off the street and out of gangs. In the boxing ring is Andre, a young fighter determined to stay away from gang violence. But when word comes in that Andre's brother has been shot and killed by a rival gang, Andre swears to avenge his brother's death. Chase and August try to persuade him to let the police handle it, but Andre slips from their grasp in pursuit of the killer. The incident also brings back memories for Chase, who is struggling with unresolved guilt over his former partner's murder by a gang youth.