The firehouse is on high alert when mysterious threats begin to emerge throughout Chicago. The situation turns dire when news of a mass shooting brings members of squad and truck into the middle of a dangerous and harrowing scene. Lt. Casey works diligently to investigate the missing money from the fundraiser for the victims of the recent tornado. Meanwhile, Jimmy agrees to represent the firehouse in the first annual "Battle of the Badges" boxing match against the 21st district police department and Chili's erratic behavior continues to be a major issue for her ambulance partner, Brett.
No job is more stressful, dangerous or exhilarating than those of the Firefighters, Rescue Squad and Paramedics of Chicago Firehouse 51. These are the courageous men and women who forge headfirst into danger when everyone else is running the other way. But the enormous responsibilities of the job also take a personal toll.
With big reputations and hefty egos, the pressure to perform and make split-second decisions is bound to put squad members at odds. When a tragedy claims one of their own, there's plenty of guilt and blame to go around. In the middle of a divorce, Lt. Matthew Casey tries to go about business as usual, but can't help butting heads with the brash Lt. Kelly Severide of the Rescue Squad - and each blames the other for their fallen team member. When it's "go-time", though, they put their differences aside and put everything on the line for each other. This is a look inside one of America's noblest professions.