Uniformed patrol officers and detectives in the Chicago Police Department's 21st District, with a focus on the Intelligence Unit's fight against major crimes like organized crime, drug trafficking, and high-profile murders.

Two teenage girls have gone missing and the team know the clock is ticking to find them. Halstead, Dawson and Lindsay investigate a tenement which gives them a much needed lead. Voight brings the father of one of the girls to district in order to get some honest answers. Meanwhile, Platt puts Roman and Burgess on gun buy-back duty where they ask questions when they aren't supposed to.