Tracy Spiridakos

An entire apartment complex is forced into quarantine when cases of the deadly virus turns 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.

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.

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

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.