The mattress factory fire spirals out of control; truck and squad lay it on the line in hopes of getting the trapped victims out alive.
Severide and Kidd continue to investigate Benny's old arson case; unexpected news leads Brett to ponder a big decision; all hell breaks loose.
A serial arsonist cold case is reopened when Lt. Severide finds a connection to a recent salon fire; Firehouse 51 celebrates a retirement party.
Severide must make a tough decision about the future of his career at Firehouse 51; Herrmann deals with the consequences of his temper; Cruz is excited to demonstrate the Slamigan at the Firefighting Expo; Commissioner Grissom returns.
Dr. Charles and Dr. Reese search for answers when a mother claims her daughter is possessed; Dr. Rhodes and Dr. Bekker must find a way to save a pair of conjoined twins; Dr. Halstead struggles to get Dr. Manning's attention.