'Chicago' Shows Team up to Fight Graphic Infection Crisis, and Fans Have Too Many Feelings

Flesh-Eating Bacteria

The episode did not shy away from showing the graphic devastation of the mysterious disease from the first few minutes of the crossover. As many of the franchise's beloved characters tailgate before a football game, a man collapses and Natalie (Med's Torrey DeVitto) finds a massive injury in his body that is covered with decaying skin.

The doctors at Med diagnose the man with Netcrotizing fasciitis, a flesh-eating bacteria condition that is very rare and not contagious. The chances of another person getting the infection is astronomical. Little did they know, however, the disease would set the stage for a massive outbreak that would send Chicago into a panic.

Spreading Fast

It's not long before Brett (Fire's Kara Killmer) and Foster (Annie Ilonzeh) respond to a call from a house where a couple has been dead for some time. Their bodies are also being eating by the strange bacteria.

Burgess (P.D.'s Marina Squerciati) also responds to a woman who parked in a gas station and just stayed there. Her face was almost entirely eaten away by the bacteria, but she was still alive when Burgess called for the paramedics. Her baby was also in the car wit the deceased and they were both revealed to have died later in the episode.

Burning the Evidence

Things take a tragic turn when Firehouse 51 responds to a fire at Central Chicago University's Science Building. The action-packed rescue mission comes with its hurdles, as the scientists' tell the firefighters to protect the second floor at all costs.

The second floor's fire is a strange green color, and the connection to the company BTR — which the first victim kept chanting before they died — made them think the incident had been a deliberate attempt at hiding evidence of bioterrorism.

At this point the doctors are able to identify the bacteria causing the dangerous infection but have no way to properly treat the spread other than surgery and more people are getting sick.

Ground Zero

While leaving Med, Brett and Foster realize all of the paramedics leaving the hospital are heading toward the same apartment building with cases of the strange infection. While they don't know the connection between all affected, the number of patients makes them believe this might be ground zero for the bacteria.

Doctors, firefighters and police team up to search the building and interrogate the people who live there during a tense evacuation.

The people say they noticed an exterminator spraying a substance earlier that day, but didn't ask too much about it. Upon further infection, Will (Med's Nick Gehlfuss) and the team find the mysterious man burned the spraying equipment after putting the infection all over the walls. The discovery officially makes what happened an act of terrorism.

Quarantine Chaos

Sharon Goodwin (Med's S. Epatha Merkerson) orders all the apartment tenants to quarantine, along with Upton (P.D.'s Tracy Spiridakos) who feared she had contracted the disease after a former assistant at the science building collapsed on her.

The media reports on the outbreak, combined with the isolation and one rowdy tenant causes panic in the quarantine area. The moment reaches peak stress levels when the people start chanting "Let Me Out" and eventually just storm out of the safety zone to safety as Dr. Charles (Med's Oliver Platt) and Sharon watch in horror. Upton and the teenage girl next to her decide to stay though, where it's safe.

The Big Twist

Will and a CDC doctor, who happens to know him from college, work together with some biologists from the university to figure out a treatment for the devastating infection.

The Intelligence unit later uncovers through their investigation that one of the biologists actually has a bone to pick with the big corporation, and he is the likely suspect of the crime. The biologist is then seen asking his partner to leave him alone in the Med lab and he sabotages with the samples of the bacteria.

Will walks in at the right time and tries to stop him, but he injures him and gets away.

The episode then turns into a manhunt for the disgruntled biologist who unleashed the bacteria in the city.

Amanda

Haley's teenage friend from quarantine was one of the few victims of the infection that was caught early enough to possibly save her. Dr. Marcel (Dominic Rains) and April (Yada DaCosta) successfully remove the infection without her losing her leg, but she keeps crashing while in recovery.

Natalie and Haley stay vigilant on her condition, but they are convinced that she will be O.K. The episode ends on a rather happy note with her when she wakes up, healed and reunites with her grandmother.

Why He Did it

The manhunt for the biologist leads them to his ex-wife's house and she is hiding in an underground bunker in their basement. She fires at them with her gun when they get it open, but eventually manage to calm her down. When they interrogate her she refuses to believe he caused the outbreak, but reveals he said he had one more target before he's done.

Intelligence follows the clues to the BTR Industries offices, where a board meeting is set to take place. They all rush to evacuate the building and hopefully catch the guy before any more people get hurt. Just in time too, as Will and the CDC doctor finally find a set of antibiotics than can treat the dangerous disease.

They find out that the company cut his research funding for dangerous bacteria, and that is likely why he snapped and planned the dangerous attacks on the city.

Boardroom Standoff

Jay (Jesse Lee Soffer) is the first to find the man, who is holding the board members hostage and killing them one by one with the disease and guns. Jay talks him down while Upton prepares to shoot him from another building, and Voight (Jason Beghe), Will and the others rush toward the scene.

The man admits after they cut his funding he decided to show them why they made a mistake, by inflicting a deadly disease on the city. He is about to force Jay into infecting himself with the bacteria, when the team distracts the man with enough time for Voight to storm in and kill him.

After the emotionally-taxing few days, the episode ends with the different teams dealing with the events of the day on their own. Sharon reflects in voiceover about how the best teams work together as families.

What did you think of this year's big crossover? The One Chicago shows air Wednesdays on NBC starting with Chicago Med at 8 p.m. ET, followed by Chicago Fire at 9 p.m. ET and Chicago P.D. at 10 p.m. ET.