'Chicago Fire,' 'Med' and 'P.D.' Team Up to Fight Flesh-Eating Bacteria in Crossover Sneak Peek (Exclusive)

ET exclusively debuts a first look from Wednesday's three-hour crossover event.

A deadly bacteria is taking Chicago hostage. 

On Wednesday's three-hour One Chicago crossover event, titled "Infection," the teams from Chicago Fire, Chicago Med and Chicago P.D. gather together to formulate a game plan to eradicate a rare and fatal bug as it begins to quickly take the lives of innocent victims around the Windy City. But members of the Chicago first-responders begin to have suspicions that there may be something bigger at play when they discover the victims all live in the same apartment building.

In ET's exclusive sneak peek from the crossover's first hour, which kicks off on FireMed doctors Natalie Manning (Torrey DeVitto) and Will Halstead (Nick Gehlfuss) report back their findings on the John Doe who was admitted to the hospital after he began exhibiting severe symptoms from the dangerous bacteria that's rapidly spreading. 

"All he said was BRT," Fire's Matthew Casey (Jesse Spencer) communicates the patient's last words, causing Will to rethink what may have caused this.

"He has a severely infected leg so we're running a culture to see if we can pinpoint the pathogen," Natalie says to the rest of the team.

"Although seizure isn't normally a symptom, the visual presentation and the speed with which the infection is spreading indicates this bug is causing necrotizing fasciitis...," Will adds, expecting everyone to understand just how dire the situation is. But when blank faces stare back at him, he uses layman's terms instead: "More commonly known as flesh-eating bacteria."

Casey, along with Fire's Sylvie Brett (Kara Killmer) and Kelly Severide (Taylor Kinney), and P.D.'s Jay Halstead (Jesse Lee Soffer) all react with horrified expressions on their faces at Will's revelation. And Natalie's attempts at downplaying the non-contagious nature of the mysterious disease doesn't exactly lessen their worries.

"How do you get nec--," Severide asks, before Will cuts him off to explain how one would even be infected with flesh-eating bacteria. Basically, it's not a great situation to be in. 

When the Med docs emphasize their need to find out who their John Doe is so they can treat him back to health, that's when P.D. comes in. But it's not going to be easy for Jay to get an I.D. with literally nothing to go on. Will the One Chicago team figure out what's going on before it's too late? We're going to go out on a limb and say yes!

Watch the trailer for the One Chicago crossover event below.

The three-part One Chicago crossover kicks off Wednesday, Oct. 16 at 8 p.m. ET/PT on Chicago Fire, followed by Chicago Med at 9 p.m. ET/PT and Chicago P.D. at 10 p.m. ET/PT, on NBC.

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