When Kelton is found murdered, Voight's grudge against the mayor-elect puts him under suspicion. Upton and Halstead are eager to prove their sergeant's innocence, but the more evidence they gather, the closer they come to doing the opposite.

When Atwater goes undercover in a dangerous South Side drug syndicate, he learns there may be more to its kingpin than meets the eye. Halstead tries to join Atwater undercover, but finds himself at a disadvantage. Voight petitions the brass to show Ruzek leniency in his court case.

The shocking murder of young boys affects Halstead. Crawford encourages Intelligence to use a new facial-recognition software to help identify a suspect, but the plan backfires.

Voight pulls Darius in after Crawford asks Intelligence to investigate a dangerous drug, but there is little trust in the relationship. When their plan to nail a dealer goes awry and another CI is murdered, the team must make a tough decision about Darius.

As they await news of Halstead’s fate, the team tries to focus on work, turning their attention to an illegal arms dealer. Atwater discovers his brother, Jordan, is back in Chicago and could be tied to the case. Voight faces the tricky task of how to deal with Halstead’s shooter. Burgess finally makes her decision.

Voight makes a deal with Darius Walker to help bring down a rogue group of dirty cops dealing drugs that were supposed to be destroyed. Upton clashes with Voight and enacts her own form of justice.