Two months after the fire from the season 5 finale, Firehouse 51 is gathered to honor Matt Casey...who is still alive. Gabby's dad beats an almost suspiciously hasty retreat from Casa Casey, and there's rumors that the brass has their eye on the former alderman for Captain. Everything seems good between the favorite couple, but Gabby has some unresolved issues stemming from Matt's goodbye to her in the fire. She ignores her dad's advice and dodges the chaplain, but ultimately comes clean with how she's feeling to her husband. Everything's good in paradise again. 

Cruz is sucking up to Mouch after his heart attack, and Mouch is eating up it...along with power smoothies and chia seed sandwiches. Hermann and Otis are both embarrassed for Joe, but Mouch pretends that everything's normal. There are lots of good bits about Cruz's adoration of Mouch and Mouch's commitment to his new healthy lifestyle. Still, everybody groans and rolls their eyes when Mouch signs the house up for the Bucket Brigade, until he gives a moving speech about how he was ready to retire before the big fire, and how he values the time he gets to spend with his firehouse family. Casey makes it a mandatory event.

Brett's high school bestie is in town, and Otis and Cruz are both into her. Too bad she has her sights set on Kelly, especially even after Brett warns her about his recent heartbreak and his player ways. She might run into some resistance from his new roommate though. Stella has been evicted from her place after pushing the landlord too far, and is now crashing with her erstwhile lover. Drama is sure to ensue.

Donna has switched schools to teach teenagers instead of fourth graders, and of course there's an explosion in the chem lab on her first day. She's rescued after going into the fire after a fellow teacher, and tells Boden that the fire was no accident.