Tracy Spiridakos

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.

Mouch builds a classic firetruck model for the Deputy District Chief, but quickly needs some assistance from Gallo and Ritter. Brett and Violet encounter multiple victims with a strange set of symptoms. The results of Cindy’s chemotherapy loom over the Herrmann family.

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.

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 a deadly virus turn into an epidemic; P.D. chases a lead that could point to a case of bioterrorism, and Will gets dangerously close to the suspect.

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