Inside the Three-Part One Chicago Crossover

The three-part One Chicago crossover brought Chicago Fire, Chicago Med and Chicago P.D. together, with Detectives Jay Halstead (Jesse Lee Soffer) and Hailey Upton (Tracy Spiridakos) returning to the city. A tragedy on a commercial flight set off a frenzied hunt for a criminal harboring a deadly nerve agent, and several members of the Firehouse 51 family wound up in the hospital under the care of the Gaffney doctors.

Halstead and FBI Special Agent Upton proved pivotal in resolving the crisis. P.D. showrunner Gwen Sigan said, "It just felt like the Super Bowl's halftime show, it just adds something extra." The reunion also gave the former partners the on-screen closure they missed: "They left the show in different years, so they didn't get to leave as partners," she said, and the crossover allowed scenes the characters never had before.

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