Veteran Chicago Police Detective Jarek Wysocki leads the special unit fighting against the corruption. Wysocki is assigned to head the special unit by his boss, the newly appointed first-female Chicago Police Superintendent and his one-time partner, Teresa Colvin. Also on the unit is Caleb Evers, a young detective and Wysocki's latest partner.
During their investigations the detectives often encounter police officers Vonda Wysocki (Jarek's niece) and Vonda's partner Isaac Joiner. Undercover officer Chris Collier, who goes by the name Liam Hennessey while undercover, works the streets as he gets information on Hugh Killian and the Irish mob and their connection to the corruption. Believed to be source of the corruption is Alderman Ronin Gibbons, a powerful and influential politician in Chicago.