Detectives Briscoe and Green investigate when a masked schoolkid opens fire on classmates, killing four and wounding eleven. It soon becomes apparent that more than one child fits the profile of a youth capable of committing such violence. An e-mail sent by one of the students skews the investigation towards one particular youth with a violent history. But finding the perpetrator becomes a race against time when another e-mail arrives threatening more murders. E.A.D.A. McCoy goes head to head with Jamie Ross (Carey Lowell), who is acting as the teen's defense attorney, and who argues that the e-mail is inadmissible because it is privileged.

A woman's murder leads Briscoe and Green to discover the actual target was a reporter who did a story about voting improprieties in a recent senatorial election. Carmichael can't get the reporter to reveal her sources for a story containing allegations that the vote was fixed and ballots tampered with, even though the reporter's life is at risk. Without the source, McCoy and Carmichael have a difficult time making a case against the Senator, who they believe has ties to the mob and ordered the hit on the reporter. The case hinges on 2,000 missing ballots from the vote that were stolen by the mob. Once the ballots are found, there is a court battle over whether or not they should be counted. McCoy believes that the ballots will show the Senator's motive for ordering the hit, but an appellate court won't allow it, so their case is virtually dead. In the end, McCoy is able to convince the reporter to reveal her source and have him testify against the senator, which surprisingly turns out to be the Senator's own assessor. Meanwhile Carmichael tells McCoy that she is leaving the D.A.'s Office to accept a job with the U.S. Attorney's Office as soon as the case is over.