Lt. Casey returns to work at Firehouse 51 after nearly being killed in a building collapse and Shay meets Allison Rafferty, her new partner, who is friendly to everyone except…

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.

A pest control problem forces the 51 team to temporarily bunk with Firehouse 20. All under the same roof, Casey clashes with Capt. Delaney while Foster, Kidd and Brett fear…