Daniel Kyri

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.

Brett and Foster question the suspicious circumstances surrounding an attack at a juvenile detention center; a convoluted new technology at Firehouse 51 tests everybody's patience; Kidd is chosen to represent the district at a leadership conference.

A series of mysterious gas leaks has members of Firehouse 51 puzzled and spread thin; Brett's conflicted when her birth mother gets serious about finding her; Severide misunderstands his role as Cruz's best man; Mouch bites off more than he can chew.

A series of teen opioid overdoses sees Severide partner with Sean Roman, but he begins to suspect there's more to the story than his old friend is telling him; Casey tries to be there for Brett as she considers her birth mother's offer to meet.

Severide teams up with Seager and the OFI when a motel structure fire turns suspicious; Firehouse 51 members become amateur sleuths following a Reddit post involving one of their own; Brett continues to get invested in her birth mother, Julie.

Casey struggles to get Boden to sign off on an energetic new recruit; Foster extends an olive branch to her irritating new medic; Otis inspires Herrmann to seek new partners at Molly's; Brett realizes life in Fowlerton will take some getting used to.