Severide and Kidd continue to investigate Benny���s old arson case, unexpected news leads Brett to ponder a big decision and all hell breaks loose as the season concludes.

Severide and Kidd continue to investigate Benny's old arson case; unexpected news leads Brett to ponder a big decision; and all hell breaks loose as the season concludes.

A serial arsonist cold case is reopened when Lt. Severide finds a connection to a recent salon fire. Firehouse 51 celebrates a retirement party.

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 and Boden search to uncover whether arson was the cause of a fire at a hair salon. Mouch, Herrmann, Otis and Kidd make a startling discovery in tracking down a missing piercing nozzle.

Severide and Boden search to uncover whether arson was the cause of a fire at a hair salon. Mouch, Herrmann, Otis and Kidd make a startling discovery in tracking down the missing piercing nozzle from Engine 27.