Tracy Spiridakos

Kidd and Severide's honeymoon is interrupted by a dangerous person from their past. Kidd's former academy classmate joins Firehouse 51. Brett and Violet reflect on their relationships.

Firehouse 51 is called to an airfield when a passenger jet goes silent mid-air, triggering a high-stakes emergency and cracking open a bigger mystery that could put countless lives in jeopardy.

Chief Boden unwillingly agrees to let Dawson and Brett go undercover; Kidd and Zach's relationship hits a bump; Cruz has a hard time expressing his true feelings for Brett.

Tensions run high between Casey and Herrmann when the firehouse responds to an apartment complex fire. After discovering something extremely suspicious during the call, Kidd and Severide do some investigating and get CPD on the case.

Mouch and Ritter work together to solve a murder mystery; Severide and Cruz tackle a food truck fire; Gallo goes to see Hawkins about Violet.

An entire block of flats is forced into quarantine when cases of the deadly virus turn into an epidemic.