After heroically saving a mother and newborn baby from a rooftop fire, Kidd receives surprising news: she's being transferred. Severide and Casey believe something is off about the turn of events, prompting them to investigate. In other events, Otis and Herrmann discuss the possibilities of taking over a rundown bar and Dawson's frustration with her father reaches a boiling point
Casey and Severide collide after Casey argues with him over the best way to save a teenager entangled in barbed wire. Casey looks to Boden for help, but realizes that he will have to fix the situation by himself. Elsewhere, Otis tries to convince Casey to participate in the beta test for an expensive piece of new firefighting equipment imported from Japan. Meanwhile, Kidd and Hope come to blows over a payroll issue; and Brett goes on a date with a doctor she meets during an ambo call.
While running a secret errand, Dawson finds herself trapped in a collapsed parking structure. In other events, pressure mounts on Casey as he takes on additional duties; Kidd grows skeptical of Hope; and the firehouse receives a surprise visitor.
Lt. Casey gets off on the wrong foot with Sam Mullins, a temporary chief who is filling in for Boden at House 51 for the morning. When Casey later makes a risky move in an attempt to save a distraught man from jumping off a building, Mullins has a surprise that Casey does not expect. In other events, Mouch flies in Cruz's brother as a birthday surprise, but the rest of the squad struggles to keep it a secret; and Brett is caught off guard when she learns new information about Hope.
After learning the school fire wasn't an accident, Chief Boden turns up the pressure to investigate the cause of the fire that trapped his wife. Meanwhile, Mouch pushes all of the wrong buttons in his efforts to win the competitive challenge known as the firefighter muster.
Season 6 opens with most of the squad still trapped inside the warehouse fire and Chief Boden making a risky last-minute decision in an effort to save them. Dawson, meanwhile, continues to deal with her father, who has new plans for himself; Brett's childhood friend Hope visits the Windy City and strikes the attention of someone within the firehouse; Kidd goes head-to-head with her landlord; and a fire at a high school hits close to home for Boden.