Brettsey’s other half will leave the Windy City.

The upcoming 12th season of “Chicago Fire” will be the last for Kara Killmer, who plays Sylvie Brett. Although Killmer will appear in the first part of the season, it has not yet been determined how many episodes she will appear in.

Killmer joined the NBC procedural show in Season 3 in 2014 and appeared in 193 episodes. She also had recurring roles on the spin-offs “Chicago Med” and “Chicago P.D.” All three shows are produced by Wolf Entertainment and Universal Television, a division of Universal Studio Group.

During Season 10 of the series, Jesse Spencer, who played Matt Casey, Brett’s boyfriend, left the show. In Season 11, while Taylor Kinney was absent due to personal matters, Spencer appeared numerous times. In the final moments of the season finale, Casey – who lives in Oregon – proposed to Brett.

Amid Hollywood’s twin strikes, Season 12 was of course delayed. The writers room reopened on October 4, and production on “Chicago Fire” is expected to begin the week after Thanksgiving.

As Variety previously reported, Kinney will return for Season 12 after missing the final eight episodes of Season 11. Behind the scenes, Andrea Newman, who previously ran the writers room with series co-creator Derek Haas , will be the solo host.

Elsewhere in the One Chicago world, Tracy Spiridakos, who plays Hailey Upton, is leaving Chicago P.D. after the upcoming 11th season, following in the footsteps of her on-screen husband. Jesse Lee Soffer, who plays Upton’s husband Jay Halstead, appeared in Season 10. It has not been revealed how many episodes she will appear in.