Haley and Veronica Song are brought into the hospital. Veronica is unconscious. Will realizes that Haley has been exposed.
Sharon talks to a bunch of reporters and says the disease is only fatal if not treated.
Marcel wants to remove dead tissue from Veronica before sending her to the ICU. Meanwhile, Manning finds that Haley did have an open cut on her finger.
Veronica dies in surgery while Goodwin watches from outside the OR.
Dr. Danover from the CDC shows up and it turns out she knows Will. He is made liason for the case. Andrea wants to talk to Veronica but she's already dead.
Chicago Fire is called to an apartment where they find two more victims. Chief Boden wants to know how this is possible and isn't happy to hear that Chicago Med has theories but no answers yet.
Sharon sends Maggie home and sets up a quarantine.
Everyone in the apartment building is evacuated and quarantined but one woman doesn't want to go. She later tells Dr. Charles that she knows the CIA is making everyone sick to see what happens.
Jay Halstead updates Haley, who is quarantined.
A guy comes to PD. He tells Trudy, who passes it on to Voight, that he interviewed to babysit the baby that died. While he was there, the mother got into a fight with an exterminator. They lived in that apartment building.
Haley meets a 15 year old named Amanda in quarantine. Amanda is sure 9th grade was easy for Haley.
PD learns that Stuart Anderson was not the person making threats. His IP address was spoofed.
Natalie says Amanda seems fine so far but she will check on her later. She asks Haley how she is. Haley is fine and asks Natalie about her TBI. Natalie is fine also.
Amada asks Haley when she decided to become a cop. Haley tells her about her dad's store getting robbed when she was 12. She wanted to be a badass like the sergeant. Amanda thinks she is. Haley doesn't think so.
A sweep of the apartment building yields a sprayer in the furnance that contains the bacteria. Will realizes this was a terrorist act.
Will and Andrea talk. She used to have a crush on him. Their personal convo is interrupted when they both realize the bacteria is reproducing super fast.
Voight wants to talk to the potential victims. Dr. Charles is against it. Voight says Charles can come with him but he has to talk to them to find out who the originator of this thing is.
Haley feels like she needs to do something. She and Charles interview some of the tenants. Charles wants to talk to Charlene alone.
The research scientists recognize the bacteria. They were researching antibiotics to it but they lost the data in the fire. They reluctantly agree to help.
Another victim dies.
Charles talks to Charlene who says he knows all about the CIA but gives him some info about the phony exterminator's vehicle.
A man in quarantine develops the illness and Amanda freaks out. Haley helps her calm down.
PD starts looking for the perp's vehicle.
April wants to try to save the latest victim's arm. He wants to be a firefighter. But in surgery Marcel discovers the entire arm muscle is dead.
Sharon is upset that the news has edited her interview to make it look like she has no suggestions for how people can avoid getting sick. Meanwhile, Charlene starts a mutiny, saying they are all going to get sick if they stay in quarantine. Most of the tenants agree with her and they all rip their plastic and run away, except for Amanda, who Haley convinces not to listen.
The escapees are quickly rounded up except for Charlene and a few others. They are angry that they are being forced to stay in quarantine.
Marcel does his best to encourage Mr. Kwan, who is upset that he lost his arm. He goes out of the room and April sees he is upset but he won't admit it to her.
The Mayor wants Sharon to lie on TV and say everything will be fine so that his office doesn't look bad. She refuses.
Haley is released from quarantine. She goes back to PD. Natalie sits with Amanda, who almost immediately develops the infection in her leg. Amanda freaks out while Natalie gives her an MRI.
Will works with the research team. Their proposed cure slows the infection down but doesn't cure it.
Haley tries to reassure Amanda before her surgery.
There's wall-to-wall TV coverage. A conspiracy theory site accuses Mama Garcia of spreading the bacteria as part of a gang plot to get revenge on America .
Fire is called out to a public disturbance.
The culprit is caught on CCTV. Ruzik realizes he works at the CCU lab.
And the perp is alone in the lab. He takes out the samples from the fridge and puts gasoline in them. Will catches him and the guy shoves him against the wall, knocking him out...