A month after a devastating loss, firefighters of the Chicago firehouse 51 fight to work past it and continue to serve the city.

An injury sidelines Herrmann. Severide carries out a victims last wish after failing to save him. Casey wants to restart things with Hallie. The fire crew are having issues with a goat being on their insignia.

Casey is pressured into recanting a statement when he learns a drunk driver is the son of a veteran CPD detective. Severide learns the severity of his injuries. Mills wants out of the family business to pursue firefighting.

Boden faces backlash after his decision to pull his team from a burning warehouse. Voight steps up his threats against Casey. Severide suspects arson threats against an elderly lady. Leslie has an encounter with an old flame.

Kelly seeks help from his ex in acquiring painkillers. Herrmann gets stuck in a pyramid marketing scheme. The feud between Casey and Detective Voight becomes personal.

Casey reaches a boiling point with Detective Voight and gets an angel to help take him down. Dawson faces off with the suspension board.

It's Thanksgiving and Boden order's a drug test for the 51, putting Severide in a tough position. Cruz's brother is injured in a gang shooting. Otis starts a podcast. Leslie's ex-girlfriend visits the firehouse.

Mills considers leaving the 51 after encountering the remains of a victim. Leslie is confronted by Clarice's husband. Severide develops an addiction to painkillers. Dawson suspects a mother poisoning her daughter.

An injury on the job forces Vargas to retire. Cruz seeks to pull his brother from a gang and the price is high. Severide starts a relationship with a woman he saved on a job.

The 51 crew is under investigation when a woman accuses the firemen of stealing a diamond necklace from her home. Cruz makes a risky move to pull Leon out of a gang. Things get serious with Kelly and Renée.

Casey sees his mom in prison.

Dawson is stuck in a love triangle between Casey and Mills. Casey is asked to speak at his mother's upcoming parole hearing. Severide comes clean to Boden about his arm injury.

Kelly considers moving to Madrid with Renée and learns the risks of surgery. Matt speaks for his mother at the parole hearing. Boden races against the clock to save Ernie. Leslie offers Clarice a place to stay.

In the wake of a shooting that placed her brother in the ER, Gabriela seeks help from an old enemy. Herrmann learns his silent partner is a thug. Leslie and Clarice face a custody lawsuit with Daniel. Casey seeks closure.

Shay decides she wants to have a baby. Gabby, Herrmann and Otis finally name their bar. Kelly's father visits Firehouse 51. Boden hosts a Fire Academy Gala. The truth about the death of Mills' father is revealed.

Kelly pushes to get Peter on the Rescue Squad, while chewing out Casey for being around Darden's widow. A tragedy strikes the fire crew. There is a shooting at the firehouse. Herrmann tries to reconnect with his family.

Mills focusing on making squad causes a rift in the 51. Herrmann's wife comes to the firehouse and experiences complications. Shay and Dawson are having issues with the new ambulance candidate.

Severide faces a bizarre accusation and the 51 is ordered to attend a sexual harassment sensitivity seminar. Matt and Hallie reunite. Voight is released from prison and reinstated. Mills sparks Hadley's envy.

Casey must set aside his differences with Voight to find Hallie's killer. Peter is reeling from the truth about his father's death. Leslie prepares for insemination. Otis hires his Russian cousin as a waitress as Molly's is set to open.

The 51 are sent to a prison to do a job and all hell breaks loose. Cindy goes into labor. Shay learns the results of her pregnancy. Mills learns about his chances to make squad. A familiar face returns to Severide's life.