The members of Firehouse 51 struggle to cope when one of their own dies in a fire, while lieutenants Casey and Severide blame each other for the tragedy.
Severide hides his serious shoulder injury as he tries to rescue a construction worker from a collapsed building; two teens become trapped in a vehicle.
Severide is targeted by an arsonist, Battalion Chief Boden clashes with Gail McLeod, Shay has suspicions, and Mari visits Mouch.
Pete learns that Chief Boden knows more than he's letting on about the death of his father; Shay decides she's ready to be a single mum.
With tensions running high between Chief Boden and Bennie Severide, things boil over when Mills questions Bennie about the fire that killed his father.