Chief Boden is accused of leaving a homeless man to die in a warehouse fire after ordering his men to evacuate the scene, creating negative press and bad feeling within the department. Meanwhile, Lieutenant Severide helps an elderly woman facing some neighborhood problems. Detective Voight ramps up his intimidation tactics aimed at Casey in an attempt to discourage him from testifying against his son. Shay is forced to revisit her heartbreak over her ex-girlfriend Clarice, when she finds herself face-to-face with the ex and her husband during a call. Hermann’s temper flares during a rescue call at a Halloween block party.

Casey confronts Detective Voight about his harassing tactics, vowing never to back down, and ends up paying the price for his decision. Dawson faces disciplinary action for her on-the-job conduct. Meanwhile, Severide finds his arm failing him during a rescue at a construction accident, and reaches out to Anna, an old flame and pharmaceutical rep, hoping she might be able to help alleviate his injury problems.

Facing suspension, Dawson gets a hand from the same girl she saved through the procedures that landed her in front of the disciplinary board. Lieutenant Casey finds his fuse shortening as Detective Voight stops at nothing to get him to retract his statement. However, when Casey lays his life on the line during an apartment fire, he may have unknowingly caught the break he was needing.

Dawson attempts to help her brother Antonio unravel the details of his drugs-and-gang investigation, and goes behind his back in turning to an unlikely source for assistance. Casey and his mother, Nancy struggle with their new relationship. Meanwhile, as a favor to Lieutenant Whaley, Severide visits someone important from his past, while Herrmann and Otis learn some hard truths about their "silent partner" in the bar.

Accused of sexual misconduct by a former paramedic candidate, Severide faces potentially dire consequences and fights for his survival both within the Chicago Fire Department and the legal system. Detective Voight returns, looking to collect on the favor that Dawson owes him for helping her brother, Antonio. Casey falls back into old patterns in his personal life, while Dawson, Herrmann and Otis become the proud owners of a real neighborhood bar as Molly's prepares for its grand opening.

Events force Lieutenant Casey to team up with the Intelligence Unit, now run by Voight, who doesn’t appear to have changed his crooked ways after his stint in prison. Shay's excitement at the prospect of becoming a parent grows, while Mills and Dawson face some personal challenges. Meanwhile, the house comes together to support the opening of Molly's.