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.

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.

A spate of robberies comes to light after a firehouse lockbox key goes missing, and Sgt Hank Voight suspects a firefighter may be involved. With Boden's support, he recruits Cruz to go undercover to help sniff out any suspicious activity.

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

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.