The show follows the lives of the firefighters and paramedics working for the Chicago Fire Department at the firehouse of Engine 51, Truck 81, Squad 3, Ambulance 61 and Battalion 25.

A major explosion occurs at the start line of a CFD and CPD 10k charity run outside a Chicago Medical Center which Dawson and Casey are taking part in.

It sends the people of Chicago into chaos with both local and federal law enforcement agencies rushing to find the perpetrators.

Dawson is trapped under the rubble and Casey and Severide race against time to find her while their colleagues continue to assist victims above ground.

On April 26, 2013, NBC renewed Chicago Fire for a second season[23] and moved its time slot to Tuesdays at 10:00 pm EST.