A viral infection is running rampant throughout the hospital, resulting in everyone getting sick. A child sneezes on Arizona, which gets passed onto Alex, which leads to Jo, then April, then Avery all coming into contact with it in one way of another. Richard warns all doctors to be cautious.
April is assigned a young boy patient, who has skid and is highly susceptible to all types of infection. He quickly develops what appears to be a zit on his face, but it starts swelling, indicating infection. April arranges for him to be taken to an isolated room.
Leah insists that she doesn’t feel good and asks Richard if she can go home. But since they’re already several doctors down due to illness, he suggests she power through the pain. Stephanie informs Leah of the “swap monkey” deal they’ve made with each other, meaning whoever is the first to get sick, has to swap any future surgery the following week without complaint if another resident wants it. Not wanting to be the loser, Leah assures them that she’s fine.
Cristina is prepping her young girl patient for heart surgery and decides to leave Shane in charge of her conduit trial patients. She stresses to Shane that he can’t let any of them get infected or else the trial will die. He checks everyone’s temperature before allowing them into the conduit room, but is worried that it may not be enough. He then develops a cough.
Meanwhile, Derek is preparing for his speech on brain mapping that he’s about to give in front of 50 different scientists. Meredith notices that he looks a little worse for wear, but he assures her that he doesn’t get sick. Avery finds himself getting sick as well, but refuses April’s help.
Arizona introduces Alex to Doctor Oliver, who owns his own practice and assists them with a surgery. His technical and overall approach to the medical practice is very different, but comes with a lot of perks. It’s a side of the job Alex has never seen before and he likes it, which Oliver notices and offers him a job.
Jo’s patient isn’t allowing her to give him a tetanus shot since he’s very particular about what goes into his body. Jo tries to hold him down during a fit and his arm breaks due to a previous injury. Jo is afraid her temper made her hurt someone again, but Callie assures her it wasn’t her fault and shows her what it’s like to work in orthopedics. She ends up really loving it.
The sister of Cristina’s heart patient is brought to the hospital with the exact same heart condition. Owen and Cristina search through the family’s medical history to see if there’s a pattern.
Worried that his cough could become more serious, Shane asks Stephanie to take over conduit patients, promising to be her swap monkey afterwards. She agrees and the patients remain stable.
Derek proceeds to get sicker as the day goes on, which leaves Meredith to pick up the reins and do the speech for her husband herself. She shows him how it went via an iPad while he’s recuperating in a hospital bed.
April’s patient wakes up after his surgery to discover that he’s now in complete isolation. His parents can’t even come in and touch him anymore for fear he’ll catch something and die. April explains that he might have to remain in seclusion for the rest of his life due to his condition.
Jo reprimands Alex about not paying his bills, claiming that he’s developed a bad habit of putting things off. He looks at the pen Oliver gave him during his visit at the clinic and tells her that he may have found another way to make the bills go away. Clearly, he’s giving the job offer some serious thought.
When Cristina and Owen find no genetic relation to the girls’ condition, they inform the parents it could be environmental, meaning something in their home is causing them to get sick the same way. Moments later, their young son shows signs of the same condition. For once in possibly her entire life, Cristina doesn’t know what to do.