Tracy Spiridakos

The team investigates a drug deal gone bad after the body of a college student is found, while Detective Hailey Upton temporarily joins the team and finds her investigative methods clash with the Bureau's more buttoned-up environment.

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

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.

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.

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.