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One Chicago has been making changes left and right, but the latest is one from which there is no going back. Chicago Fire co-creator Derek Haas is leaving at the end of Season 11, per Variety. This isn’t just a creator leaving a series; this is a creator departing the franchise that he helped build. It also means that all of the people who helped Dick Wolf create One Chicago are gone.

Haas’ exit has wider implications, too. Variety adds that he’s not just leaving One Chicago; he’s departing the entire Wolf Entertainment company. In addition to his duties as co-showrunner on Chicago Fire, Haas is also the showrunner for Wolf’s CBS series FBI: International, the third series in the FBI franchise. For over a decade, he’s been integral to not one but two major TV brands — and at least the Chicago one will be completely different after he’s gone.

One Chicago Will Change After Derek Haas Leaves

Derek Haas’ departure marks the end of an era for One Chicago. Every creator other than Wolf has now left the building. Brandt and Matt Olmstead, the co-creator of both Chicago P.D. and Chicago Med, departed in 2017. While Diane Frolov and Andrew Schneider have been showrunners of Med since the beginning, they’re not the creators. So while it’s natural for people to move on after so many years, the One Chicago franchise finds itself without most of the main crew that made it into a successful franchise. It’s not only Dick Wolf who makes the shows work; it’s the creatives around him.

Chicago Fire will presumably be taken over by Andrea Newman, who’s been co-showrunning with Haas and around the series for years; she’ll be an excellent successor. But Haas and Brandt were the people who created the characters and the world, and Haas shepherded the show for over a decade. More than that, he was an ambassador for the One Chicago brand and an example of what a showrunner should be. One Chicago will go on like the well-oiled machine it’s become, but Haas’ exit is one more step the franchise takes away from what (and who) made it successful in the first place.

Chicago Fire airs Wednesdays at 9:00 p.m. on NBC and streams on Peacock.