News of a mass shooting brings the members of Firehouse 51 into harrowing territory; Casey investigates the missing money from the fundraiser; Jimmy participates in a boxing match; Chili's erratic behavior continues to be a major issue for Brett.
Mills works to save the life of a driver injured in a car wreck; Casey harbors doubts about Jack Nesbitt; Hermann, Otis, Cruz and Chaplain Orlovsky ready their team for the peewee hockey championship.
A building collapses and leaves dozens of people trapped and injured; Chief Boden faces a life-or-death decision in the rescue plan; Dawson continues her quest to foster Louie; tensions flare between Casey and Antonio.