The Chicago universe is changing for this year’s crossover. These Dick Wolf series started with Chicago Fire in 2012, then Chicago P.D. in 2014, and then Chicago Med in 2015. As the series have developed they have had a yearly #OneChicago crossover event. Chicago Fire showrunner Derek Haas teases that he and Dick Wolf are looking into aliens and tsunamis fro their inspiration. The crossover will involve the shows Chicago Fire, Chicago Med, and Chicago P.D. 

This year’s crossover will involve a mysterious illness that got its inspiration from from the two classic movies Poseidon Adventure and Independence Day. Haas stated, “We were thinking of the Poseidon Adventure or like Independence Day. Where you’ve got a bunch of stories – cutting to one, cutting to another – and there’s a mystery, both medical and criminal, going on that we’re trying to solve before it gets out of hand.”

Haas continues by stating, “Dick and I came up with the story, and then I’m writing the three episodes, which will be really fun. I haven’t written Med since we did the Med [spinoff] episode. But you’ll see why that’s feasible, because it’s less about each show having its own shape to it and more like all three shows really intertwined throughout. You could be watching any hour and be like, ‘Oh, wait, is this P.D.? Or is this Med? Or is this Fire?’ We’re even doing scenes that you would think would be a Med scene, but it’s in the Fire hour.” This #OneChicago crossover will spread out over three hours of television starting with Chicago Fire’s fourth episode that will lead into Chicago Med and then end with Chicago P.D. that will all take place on the same night.

#OneChicago returns on September 25 with Chicago Med at 8, then Chicago Fire at 9, and Chicago P.D. at 10.