Daniel Kyri

The surprising arrival of a new fire truck brings both joy and chaos to members of Firehouse 51; Boden and Severide are asked to make peace with an old foe for the greater good; Brett receives family news while Foster plans a party with friends.

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 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.

Firehouse 51 responds to a massive freeway accident that impacts someone close to them; Foster runs into someone from her past after a harrowing call; Casey and Naomi grow closer; Severide and Kidd's relationship is tested.

A series of false alarms at a private school hinders 51's ability to respond to legitimate emergencies; Kidd asks for ideas to surprise Severide on his birthday; Cruz and Brett rent out their extra room but get more than they bargained for.

Kidd must prove herself at the National Firefighter Leadership Conference, while the rest of Firehouse 51 is called to two eerily similar car wrecks; Mouch tries to keep the firehouse informed by starting a newsletter; Cruz deals with a heartbreak.