Chicago Fire is a revolving door. There have been tons of characters who have stuck around for the long haul, of course, but most have been written out of the show, or gotten married and moved on to different careers. We remember them, and we miss them.
Some characters, however, don't stick around long enough to solidify their Chicago Fire legacy. They were compelling while on the show, but they left so quickly that their impact is barely felt in seasons that follow. This article is meant to shine a light on them, and recount why they left.
Scott Rice

Scott Rice (Warren Christie) joined Chicago Fire during the second half of season 3. He was added to the 51 roster courtesy of his buddy, Severide, but he did not prove to be the most amicable presence. He was still reeling from the death of his wife, and there were rumors that he once threw someone out of a window.
Rice's reputation takes a permanent hit when he runs away from a fire during an emergency call. He later admitted to Severide that he was afraid to die and leave his son without parents. To the surprise of no one, he was let go.
Hope Jacquinot

Hope's tenure with Firehouse 51 was a disaster. The character (Eloise Mumford) got her foot in the door as a friend of Sylvie Brett (Kara Killmer), and eventually joined 51 as a receptionist. It didn't take long for Hope's antics to become a distraction, though. She struck up a romance with Kelly Severide (Taylor Kinney), and enacted a transfer of Stella Kidd (Miranda Rae Mayo) by forging the signature of one Chief Mullins (John Gatins). Once her ruse was discovered, however, she was told to clean out her desk.
Hope was around during seasons 6 and 8, but she was such a net negative within 51 that she has never been referenced again. Given her discomforting dynamics with everyone, I guess we get it. Probably not the most fun person for any of them to remember.
Gianna Mackey

Gianna Mackey (Adriyan Rae) was an exciting addition to the Chicago Fire team in season 9. She was a charismatic presence within the firehouse, and her friendship with Joe Cruz (Joe Minoso) made her immediately endearing to fans. Who doesn't love Cruz, right? We were ready to have Mackey around for a long time, and then she left before the season ended.
Mackey's exit was pretty unceremonious, and was seemingly spurred by Rae's decision to move on to other shows. Former Chicago Fire showrunner Derek Haas told Entertainment Weekly they are still on good terms, and even left the door open for Mackey's return in the future. We won't be holding our breath, though.
Derrick Gibson

Derrick Gibson (Rome Flynn) had a ton of potential. The character joined the firehouse in season 12, and proved to be an exemplary first responder in the field. The more time went on, however, the more his past trauma proved to sideline him. Sam Carver (Jake Lockett) pieces together that Gibson has a painkiller addiction.
The firefighter eventually slams his fist into a locker, and walks, while bleeding, to Stella Kidd to state that he can longer serve at 51. It was a shocking, sobering moment, and one that that has sadly yet to be followed up on. A shame.