7 Times One Chicago's 'Infection' Crossover Put Lives & Relationships on the Line (RECAP)

Meredith Jacobs

[Warning: The below and gallery above contain MAJOR spoilers for all three hours of the One Chicago "Infection" crossover.]

The heroes of Chicago FireMed, and P.D. unite to enjoy a little tailgating before football — and save the city from a flesh-eating bacteria.

Over the course of the three episodes, the firefighters, paramedics, doctors, nurses, and cops work together to figure out who's responsible for the outbreak that, at one point, leaves the city streets completely deserted when there should've been a parade. Though each hour includes something unique to the corresponding show (a fire, focus on the infected, and the hunt for the perpetrator), it very much feels like a three-hour movie, with plenty of crossover at every stage of the investigation.

9 One Chicago Characters Who Should Get a Crossover Romance (PHOTOS)

9 One Chicago Characters Who Should Get a Crossover Romance (PHOTOS)

Some are just unlucky in love, while it's time for others to find their match.

One member of Intelligence worries she may have been infected after getting blood from a person who was on her and finding a hangnail. At another point, one of the detectives willingly puts himself in a dangerous situation to try to save lives, all while hoping his team will come through in time.

In the end, they discover it's one of the microbiologists who worked in the lab where Fire responded to a call. He wanted to demonstrate the dangers of the virus to the world and the importance of funding for his research into antibiotics to combat the bacteria to those who'd refused him money.

The 7 Most Painful One Chicago Deaths (PHOTOS)

The 7 Most Painful One Chicago Deaths (PHOTOS)

Sometimes matters of life and death hit too close to home for 'Chicago Fire,' 'P.D.,' and 'Med.'

Click through the gallery above for the crossover highlights involving the One Chicago heroes, from times they put their lives in danger to big relationship moments.

Chicago Med, Wednesdays, 8/7c, NBC

Chicago Fire, Wednesdays, 9/8c, NBC

Chicago P.D., Wednesdays, 10/9c, NBC