Chicago Med Season 5 Episode 4 is the middle section of a special One Chicago crossover event.

The Chicago Med team must coordinate with Chicago Fire and Chicago PD after trying to help a patient with a deadly bacterial infection lands PD Officer Haley Upton in quarantine. While in quarantine, Haley befriends a 15-year-old who has nobody, while elsewhere in the hospital Dr. Charles tries to keep a potentially psychotic quarantined patient calm and Goodwin deals with media that want to capitalize on everyone's fear and a new mayor who wants to protect his office's reputation.

A CDC representative soon arrives to help contain and find a treatment for the disease, and she turns out to be an old flame of Will's. Meanwhile, the outbreak hits Dr. Marcel hard when one of his patients dies and another loses a limb as a result of the fast-spreading infection.

As the body count mounts and no cure is in sight, Chicago Med also finds itself under pressure from Fire Chief Bowen, who is worried about the safety of his firefighters. Meanwhile, Chicago PD gets a lead on who initially infected Chicago citizens, and the perp is inside the hospital.

To find out what happens, watch Chicago Med Season 5 Episode 4 online.