Chicago Fire's Casey, Severide, Brett, and Kidd; Chicago PD's Atwater, Halstead, Burgess, and Upton; and Chicago Med's Natalie tailgate before a football game.

They are having fun and relaxing until a man collapses. Everyone rushes to see what's wrong, and they find the man with an infected leg mumbling "BRT" and seizing.

The man is taken to Med, and Natalie and Will tell the group the man is suffering from a flesh-eating bacteria.

This is initially believed to be an isolated incident until four more victims with identical symptoms are found.

The doctors at Med then learn the deadly bacteria can be transmitted through contact.

Firehouse 51 later responds to a fire in the science building at Central Chicago University, where the pathogen was engineered.

As the firefighters rescue those trapped, Severide notices a sign in the basement that says the laboratory was paid for by BRT Health Industries, the same initials the man who collapsed was chanting.

Severide shares his theory with Voight and adds he believes the fire was deliberately set.

Intelligence works the case and identify the man who collapsed as a suspect, not a victim.

Intelligence then goes to talk to the man but learn he has died. They later discover a woman who worked in the lab with the dead man, and Upton goes to question her.

Upon arriving, Upton finds the man suffering from the deadly bacterium and gets covered in her blood.

Upton is then quarantined while the doctors run tests to find out if she contracted the bacterium.

Elsewhere, Cruz plans to propose to longtime girlfriend Chloe, but she decides they should take a break before he can pop the question.