I just watched Chicago P.D. 4×05 "A War Zone" https://trakt.tv/shows/chicago-p-d/seasons/4/episodes/5 #trakt
The team hunts drug dealers selling fentanyl, which has been linked to multiple overdoses around the city. Tay and Burgess discover a bloodied child who shares a twisted secret about his home life. Mouse contemplates reenlisting in the Army. Platt informs Tay about her next assignment.