Chicago Fire focuses on the professional and personal lives of the men and women who work in the Chicago Fire Department including Engine Co. 51, Truck Co. 81, Rescue Squad Co. 3, and Ambulance 61. Honestly, even two years later it's still difficult to understand the difference between trucks and engines, but we do know that they're all very important to saving lives in the city of Chicago.
The main characters are Matthew Casey and his girlfriend/fiance Hallie, Kelly Severide, Chief Boden, Gabriela Dawson, Leslie Shay and firefighters Hermann, Mouch, Otis, Mills and Cruz.
The first season of Chicago began after the Firehouse lost a brother during a fire. The ramifications of that death carried forth throughout the season as both Casey and Severide were believed to have been partially at fault for the death. How did that affect the morale of the house?
Dawson harbored a secret crush on Casey and felt some relief when Casey and Hallie had relationship troubles and she stood by Casey's side when Hallie was killed while helping police investigate a drug scandal. Severide and Shay lived together, but there was no money business as she's gay character in the Chicago world.