When the squad's rig breaks down in the field, Casey reunites with his old friend and colleague Jason Kannell from Squad 6, whose crew gets assigned a temporary change of quarters until the rig issue is resolved. Dawson and Brett serve their time in retraining, both tackling the class in unique ways. Severide tries to remedy what is going on with Anna and finds support from unlikely sources. As Connie returns from her family engagement, the crew lays bets on how long her temporary replacement Marcy will last.
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.