Jeff Lima

Tension builds when a group of rabble-rousers attempts to lock down the firehouse. Brett is faced with a monumental decision and Cruz readies himself for a big day. Gallo and Ritter attempt to launch Firehouse 51 into the social media age.

The crew of Firehouse 51 are full of festive cheer until Casey is accused of stealing a diamond necklace. Meanwhile, sparks fly between Shay and Severide.

Boden tries to keep the firehouse from closing, the romance between Dawson and Casey grows, Cruz worries about his brother's safety, and Severide and Katie make up for lost time.

Casey gets off on the wrong foot with Chief Boden's stand-in, while Mouch flies in Cruz's brother as a birthday surprise.

A spate of robberies comes to light after a firehouse lockbox key goes missing, and Sgt Hank Voight suspects a firefighter may be involved. With Boden's support, he recruits Cruz to go under cover to help sniff out any suspicious activity.

Casey's conscience gets put through the wringer when he visits his mother in prison. Cruz shares a secret, and Pete fills in for Shay in the ambulance crew.