Casey and Gabby disagree over Raul's presence at their home. When Gabby refuses to hear Matt's side of things and fails to fully express her feelings to him, things become tense. Matt ends up leaving temporarily, staying with Severide. Things only get worse when a drunken Raul causes the deal Casey just brokered with Blakesly to tank. The two have yet to patch things up when Casey is caught in a warehouse fire with no exit in sight.
Casey's also stressed because of the Blakesly situation -- the other alderman is using Trumpian techniques to wind up crowds at town hall meetings so that Casey is unable to present the merits of the bill. After meeting with Tamara and a failed negotiation attempt with Blakely, Matt violates his no city business on CFD time rule and shows up to the Town Hall meeting in his turnout gear. He reveals Blakesly's reasons for fighting against the first responders bill (money for Gold Coast beach improvements) and resigns, suggesting that Tamara be the one appointed to take his place before turning the stage over to her.
Cruz remains irrationally pissed at Mouch and for unexplained reasons, his leave hasn't kicked in yet. He has to call Leon to tell him that he'll have to take a semester off. His discontent extends to withdrawing from House and Squad social life, and getting belligerently drunk at Molly's. When Mouch has a supposed heart attack in the warehouse fire, Cruz loses it, and has to be held back to prevent him from heading in against orders.
With Cruz's unrelenting animosity, Mouch seriously considers retirement, meeting with his old buddy after a phone interview with the supply company. He gets drunk and maudlin at Molly's and Herrmann calls Trudy. Mouch confesses what's been going on with him to his wife. Right before the warehouse fire, he tells Herrmann that this will be his last shift, that he'll be retiring. He collapses as he and Herrmann are about to leave the building. They end up getting trapped, and it's unclear if Mouch died while Herrmann watched.
Herrmann bonds with a young Cubs fan that he rescued from a burning minivan. When he can't deliver on the 1988 Cubs team cards he promised (he forgot he sold them in a garage sale), he heads to Wrigley Field, bribing a guard with cookies to get in. He arranges for the kids favorite player to meet him on the field and sign his cast.