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.

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.

Halstead and Marcel facilitate a trans-organ exchange. Asher and Cuevas help a sexual assault survivor. Choi and Archer treat a patient whose case could expose a fraudulent doctor. Grant and Maggie take a trip down memory lane.

Mac joins forces with special agent Jack Dalton to recover a missing bioweapon and save hundreds of thousands of lives.

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.

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