Severide, Herrmann and Clarke knock back their sorrows at Molly's, sure that the next shift will be their last. Brian, the ex-husband of Clarke's wife, busts through the door and demands money from Clarke, claiming Laura borrowed it from him. When Brian calls Laura a whore, things get chippy fast - Herrmann and Severide struggle to hold back Clarke, who threatens Brian.
As the firehouse preps for imminent closure, Mouch reads their new station assignments - and then tears them up, pissed and frustrated. Casey echoes his emotion and rallies everyone together for one last fight to save the station. Outside, Nathan, the boy Severide saved a few weeks back (now fully recovered), starts a petition to save 51. This inspires Severide to wrangle firemen from other stations - even trainees - to help their cause.
A news flash in the common room TV alerts Mouch to the latest controversy - CPD busted Union President Sullivan for embezzlement. With Herrmann's support, he seizes the opportunity and crashes the union committee meeting to demand action on the closures. Turns out, they're on his side and already discovered McLeod's not clean - she receives a six-figure bonus for trimming the budget by 10 percent, a surefire check if she can knock out 51.
Later, Dawson receives a letter and takes Shay aside - she just received acceptance into the firefighter academy, even though she took the test eight years ago. Shay supports the move unconditionally, but Dawson struggles to make up her mind. Should she give up being an EMT? Without revealing her motive, she prods the others for their opinion on female firefighters. This proves unhelpful, although Casey suggests she wait - maybe she's rushing into this a little too fast.
Meanwhile, Cruz shuffles around the station, bummed about Zoya moving back to Russia and his brother leaving Chicago. His loneliness dabbles in depression - until he lands on a brilliant idea. What if he and Otis become roomies? Otis loves the idea, and the two agree to move in. But elsewhere in the station, the outlook is bleaker - Antonio drops by to say McLeod's criminal record is clean... then turns to Clarke and asks about the run-in with Brian at Molly's. Clarke bristles at the question and describes it as an argument. Antonio warns him to be honest, because Brian's dead.
McLeod turns up, and she's greeted by a crowd of firefighters and members of the community, all chanting "Save 51!" Before she can react, she and Boden are pulled into a meeting with - of all people - Senator Wheeler and Isabella. The senator believes saving the station looks good for the city - and his campaign. With the some strong-arming from Isabella, McLeod reluctantly signs away the closure. Boden holds back tears as she exits for the last time and thanks Mills for his help. Firehouse 51 will live on...
Back at the station, everyone celebrates the victory - until Shay interrupts and forces Dawson to announce her acceptance into the academy. There's an awkward pause - and then huge congratulations! Except from Casey, who later admits he wants Dawson to spend more time thinking about her decision. Is this their first real spat? Before the moment escalates, the alarm sounds.
An apartment fire rages across 16 units, with families stranded in rooms throughout. As they carefully rescue each person, Boden notices black smoke emerge from the rooftop - he calls out an evacuation. Seconds later, Casey learns a baby remains inside. He ignores the evacuation and saves the baby, but right when he finds an exit - a beam collapses on him!
They rush an unconscious Casey to the hospital, and he enters emergency surgery. Dawson cries as she watches the nurses prep him for the procedure, uncertain if he will live. Antonio visits her, but after consoling his sister reveals he has an ulterior motive - Clarke's an official suspect in the murder of Brian Hayes.
On the verge of closure, Firehouse 51 bands together in a fight to save the station.