Wanting (S05E04)

After a shooting in a tenement building uncovers the body of a slain gang leader, the detectives at 15 Division must act quickly to catch the murderer and prevent an all-out gang war. With the killer targeting the sole witness who could connect him to the crime, Andy and her rookie partner, Duncan, find themselves facing a critical test of bravery and police integrity as they strive to protect the witness and bring the culprit to justice.