Katelynn Shennett

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 video of Casey from the roof rescue goes viral; Mouch sets up a Little Free Library at Firehouse 51; Herrmann breaks protocol.

Gallo clashes with the new lieutenant temporarily filling in for Casey; Severide closes in on a dangerous and deadly arsonist.

Kidd, Seager and Carver investigate a fire at the city stables. Kylie clashes with some of the firefighters over changes due to budget cuts. Herrmann struggles to keep it together as Cindy's condition worsens.

An annoying floater takes a romantic interest in Violet. Ritter catches a local politician in a compromising position. Mouch and Severide help Trudy with an arson investigation.

Firehouse 51 helps Herrmann put on a school fundraiser. Carver's troubled brother comes to town. A grateful citizen is determined to thank Brett and Severide for saving his life.