The investigation of Chief Boden intensifies, so the pressure is on Firehouse 51 to find evidence that could clear his name.
Patterson steps in as chief, and Dawson becomes a target of the conspiracy. Also, an act of violence changes Firehouse 51 forever.
Chief Boden is being investigated by internal affairs following complications at a call-out, and the crew become frustrated with the increased scrutiny.
Firehouse 51 responds to the scene of a harrowing blaze that endangers the lives of many, including one of the Chicago family.