Chicago Fire fans have been on a rollercoaster as Captain Matt Casey has fallen in love with Sylvie Brett, his ex-wife's best friend.
The two - known to fans as Brettsey - have become a fan favorite ship, and now showrunner Derek Haas has teased how the upcoming season nine finale will see things change for the pair.
In the recent episode, Casey (played by Jesse Spencer) had an "eye-opening" conversation with Greg Grainger over Brett, which Haas has now called an "epiphany moment" for the firefighter.
MORE: Chicago Fire boss teases major update for Kelly Severide and Stella Kidd's romance
WATCH: Chicago Fire: Casey gets jealous over Brett
"It’s really an eye-opening conversation [for] Casey because, for so much of the time, he’s just thought that his feelings were obvious, and she was hard to read,” Haas told TV Line.
"And then you’ve got this guy [who Brett] obviously had a quick romance with, but who points out to Casey, ‘Man, I don’t care what you think. It’s her. She’s in love with you.'"
MORE: Chicago Fire's Miranda Rae Mayo talks dramatic Stella Kidd episode
Brett and Grainger previously dated, but now Casey has been given advice from Grainger, where will the two go next?
Where will these two go next?
"She tried to keep her emotions in check, but sometimes she doesn’t have a great poker face, and obviously, Grainger picked up on it. And where that will go from here is a big part of the last few episodes,” Haas shared.
Haas has also promised a dramatic season finale, and it seems like fans should perhaps prepare themselves for the worst.
Chicago Fire bosses have teased a major season nine ending
In an interview with Entertainment Tonight, he shared that the final episode of the series that will air on Wednesday 26 May will have "one of these gigantic last 10 minutes that drive our audience crazy".
Asked whether the episode will include a life-or-death cliffhanger with potentially not everyone getting out alive, he teased: "Maybe... There's going to be a lot going on."
One Chicago airs on NBC Wednesdays from 8/7c.
Read more HELLO! US stories here