The show follows the lives of the firefighters and paramedics working at the Chicago Fire Department firehouse of Engine 51, Truck 81, Squad 3, Ambulance 61 & Battalion 25. Following the death of fireman Andrew Darden, loyalties fracture and divide as the leader of Truck 81, Lt. Matthew Casey, and the leader of the elite rescue squad, Lt. Kelly Severide, both blame each other. Despite the differences, the firehouse comes together after the near death of firefighter Christopher Herrmann. Candidate Peter Mills, newly assigned to the firehouse, is following in the footsteps of his father and trying to find his place in the station. With paramedics Gabriela Dawson and Leslie Shay, and under leadership of Battalion Chief Wallace Boden, the team face life or death decisions every day but look to each other like family, making sure to look out for each other, no matter what happens.