WARNING: This article contains spoilers and predictions for all One Chicago shows. Read at your own risk.

On October 16, the annual crossover event for One Chicago will finally air on small screens. While fans and viewers of all three shows are very eager to witness this year's crossover, as it may seem the usual reception, the shows' executive producers reveal that the event is much more challenging than the usual. 

According to Cartermatt, the base of the event will happen in Chicago Med's focal point. This is because a "deadly virus" will be the center of the crossover. 

During the One Chicago day, the publication was able to note Chicago Med's executive producer's hints and teasers about the most-awaited event for the franchise. It has been known that the three-hour episode is written by Dick Wolf and Derek Haas. She also revealed how they've all came up with the appropriate plotline for the said crossover. 

After Wolf and Haas accomplished writing the whole outline for the three shows, each "creative team" from respective shows were tasked to make the story work in all aspects. Later on, fellow executive producer, Andrew Schneider led the teams to work on one "framework."

At the very beginning of these tasks, it was revealed that the challenges were already apparent. It was not easy to make one framework fit all the three shows together. Nevertheless, making Chicago Med the base of the crossover, meaning a "medical story" to cover the crossover, was somehow the most applicable dynamic to create a "one big episode."

Aside from the challenges of making the story work, Diane Frolov also noted that the "creative process" was another factor. She pointed out that "communication" was crucial among all the three shows. "It's ambitious," she added.

She further went on to share that this [crossover] required them to do "long weekend" shoots. Not to mention, some of the locations and settings were done in public areas. Accordingly, everyone, including the cast, crew, writers, and directors, was "pushed" to their limits. 

The One Chicago crossover will start with Casey (Chicago Fire) and Halstead (Chicago P.D.), as per MEA World Wide. While they are busy with what seemingly looks like a football game, a man collapses in the middle of the crowd. 

Crews from Chicago Fire and Chicago Med examines him and learns that flesh-eating bacteria causes the collapse. Later on, they find out that it's not an outbreak, but an act of terrorism. Everyone from the three departments will unite to resolve the problem ultimately.