Season 4 Episode 14
"All Hard Parts"
Casey is approached about running for office; Fire and P.D. engage in a charity boxing match; Chili reaches the end of the line at 51.
A stranger reaches out to Casey (Jesse Spencer) about running for alderman. Though he's initially resistant to the idea, the urging of his friends and Dawson (Monica Raymund) inspires Casey, and he starts the petition drive to get the signatures he needs to be placed on the ballot.
Firehouse 51 and Unit 21 engage in the Battle of the Badges, a charity boxing event. With Borrelli (Steven R. McQueen) standing in for Fire and Antonio (Jon Seda) stepping into the ring for Chicago P.D., the money's on P.D., as Antonio is a former Golden Gloves boxer. Even though Borrelli and Herrmann (David Eigenberg) have a plan (basically, survive past the first round), Antonio knocks out Borrelli within the first minute of the fight.
Chili (Dora Madison) continues her downward spiral after the death of her sister and the recent friction with Brett (Kara Killmer). Severide (Taylor Kinney) reaches out in an effort to discover what's troubling her, but for Chili, it's too late. After she is caught drinking on the job, Boden (Eamonn Walker) has no choice but to fire her. Forced to own up to her problems, and with Severide's help, Chili attends her first A.A. meeting.