Severide steps in as ranking officer at 51. Kidd fights to save her Girls on Fire program.
Javi spends a couple of shifts at Firehouse 51. Kidd and Carver work together to help Carver's former boss. As Hawkins and Violet's relationship blossoms, Gallo turns his attention elsewhere.
Mouch builds a classic firetruck model for the Deputy District Chief, but quickly needs some assistance from Gallo and Ritter.
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.
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.