Tracy Spiridakos

An airfield emergency triggers a deeper mystery involving a passenger plane, propelling the Intelligence Unit into a high‑stakes pursuit of the culprit, all under the sharp eye of the FBI.

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.

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

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.

A rare but deadly bacteria takes its toll on numerous victims around the city, leaving Chicago's finest first responders to work together alongside the CDC to resolve the dangerous situation. Severide suspects something bigger is happening.

Lindsay deals with the consequences of her actions when her mother is suspected of murder. Meanwhile, Lugo gives Voight an ultimatum.