With election approaching Casey's opponent tries to fling a little mud on him by saying he intends to continue working for the fire department even if he wins, in other words, he's going to be double dipping. Which leads to the Chief coming to the station and questioning Casey's intentions which leads Casey to promise he's done campaigning but when his opponent schedules a debate, Casey finds himself in a precarious position. And when the squad goes a reported gas leak, they find the remains of a child in the chimney. They break it to get to the remains. Later a detective shows up to tell Severide because of what he did, the evidence was compromised. She then shows him crime scene photos and Kelly thinks he knows who the child is--a child who went missing a few years ago. Problem is that the child went missing at a location far from the house. The detective wants to be sure but Kelly goes to see the girl's mother to tell her that he might have found her daughter. And the detective ...