Caitlin Carver

Officer Cooper clashes with his new "boot" -- Gary Steele, while Lydia Adams tries to balance detective work with motherhood.

Leslie tries to complete some of her biggest city council goals, like hosting an NFL Play 60 event with the Indianapolis Colts, and trying to add fluoride to Pawnee's drinking water.

Leslie fights with Ben over questionable sales techniques at the local farmers market.

The big wedding day arrives and Firehouse 51 welcomes Casey back to celebrate the joyous occasion; Emma's plans to replace Violet come to a shocking end.

Det. Pryma's case comes to an explosive end with Kidd and Carver's lives in danger. Brett installs an infant Safe Surrender Box at 51. Violet is determined to take Emma down.

Severide struggles with the cost of helping Det. Pryma with the Martucci case. Gallo campaigns for Herrmann to represent 51 at the National Firefighter's Association's Winter Conference. A familiar face makes a shocking return.