Chicago Fire picked up right where it left off with "Post Mortem." The dramatic episode concluded with Jack Damon (Michael Bradway) suffering serious lung damage on the job, and being told that he may never be able to fight fires again. The episode "Permanent Damage" explores the paranoia and fear that Damon has about his condition.
Kelly Severide (Taylor Kinney) paid his half-brother a visit, and urged him to be optimistic when it comes to his recovery. Damon's future depends on whether he can pass certain tests, and the 51 vereran told him that he's seen several firefighters recover without any difficulty. Severide is riding solo this episode, as Stella Kidd (Miranda Rae Mayo) is attending a training course in Maryland.
Kidd may be absent, but her departure proves to have ripple effects throughout the rest of the episode. Severide noticed a girl named Natalie walking around the firehouse, and recalls she was part of a family who lost their home in a fire a decade ago. Natalie wanted to talk to Kidd (the one heeded the initial call), but upon learning that the latter was gone, she told Severide she has more information about the fire. "I think my sister started it on purpose," Natalie alleged. This leads Severide to reopen the case.
Violet reconnects with Carver after his rehab stint

We also learn that Mouch (Christian Stolte) wanted to go to the training course, but Kidd received the necessary recommendation from Chief Dom Pascal (Dermot Mulroney). It doesn't take much to infer that this was partially informed by the frigid relationship Mouch and Pascal have had over the past few episodes.
Not only has Mouch called Pascal's leadership question, but he turned down an offer for a promotion at another firehouse. Pascal thought that the firefighter wanted to advance his career, and lined up a great gig with a friend of his, but Mouch wanted no part of it. He wanted to stay put at 51, and Pascal was subsequently embarrassed for putting in a good word.
Severide's investigation is paralleled with the one conducted by Violet Mikami (Hanako Greensmith). She went on a quest to determine why a medic abandoned a patient and nearly got them killed, and a returned Sam Carver (Jake Lockett) agreed to accompany her. It's a good thing too, because Violet and Carver were confronted with a shotgun when they went around asking questions.
Violet went full-on detective mode (with help from Carver), and eventually determined that the medic who nearly killed their patient went by the name "Danny." Unfortunately, the police repercussions are not as severe as she initially thought they would be, and the patient in question refused to press any charges. A frustrated Violet eventually confronted "Danny" and urged to him to take early retirement. With Carver at her side, Violet said she will spring into action and get arrested if "Danny" decided to put any more patients at risk.
Novak strengthens bond with Ritter and Damon

Carver and Violet still have feelings for each other, and it seeps out during "Permanent Damage." The former told Violet that he's never met anyone as "fierce" as her, and he also notes that 51 would never be the same without her. These comments definitely sting, as does the hug they share earlier in the episode, due to the fact that we know Carver is leaving the show soon.
Mouch, meanwhile, decided to work extra hard in the firehouse as a way of showing Chief Pascal that he meant business. The decision pays off, as an impressed Pascal decided to put his name in for the conference. In a somewhat surprising turn of events, however, Mouch talks badly about Pascal behind the Chief's back, and urges Herrmann (David Eigenberg) to take his position. Nothing gets resolved here, and it's clear the show is setting up a confrontation between these three men as the season draws to a close. We're here for it, even if it doesn't cast Mouch in the best light.
We're more pleased to report that we got a scene between Damon and Lizzie Novak (Jocelyn Hudon). These two had a fling, then called things off, and then Damon suffered his potentially career-ending injury. The two shared some flirty banter when Novak came to visit him in the hospital, and she was present when the doctor informed Damon that he's expected a make a "full recovery."
Damon got dismissed from the hospital, and a giddy Novak invited him over to her place for dinner. It's a huge fun for shippers of these two, and it also provided the first glimpse at Novak's dynamic with her new roommate: Darren Ritter (Daniel Kyri)! We know Ritter is not set to return next season, but we cannot deny him and Novak being roommates is a fun dynamic we hope to see more of in season 13.