The family inside Firehouse 51 knows no other way than to lay it all on the line for each other. Captain Matthew Casey (Jesse Spencer) leads the Truck Company and brash Lt. Kelly Severide (Taylor Kinney) runs the Rescue Squad.

The firehouse also includes Battalion Chief Wallace Boden (Eamonn Walker), a fireman's fireman. As chief of 51, Boden keeps his house running smoothly and his firefighters prepared to overcome all adversity. Paramedic Sylvie Brett (Kara Killmer) returns alongside seasoned veteran Christopher Herrmann (David Eigenberg) and resourceful firefighter Stella Kidd (Miranda Rae Mayo). New to the firehouse is Emily Foster (Annie Ilonzeh), who is intelligent, easygoing and teams with Brett.