A virus breaks out at Grey Sloan Memorial Hospital. Because of the close encounters of doctors and patients, the virus spreads like wild fire. It first knocks out Jackson, then Leah, and finally Derek. It's an inopportune time for Derek to get sick because it's the day of his presentation on brain mapping; to fill in for him, Meredith steps up and delivers her own twist on his speech. Callie teaches Jo about the joys of ortho and how it presents the opportunity to take out all frustration on the patient while helping them, plus it pays. Cristina and Owen team up to work on a pair of sisters who have cardiomyopathy caused by an unknown source, and even though they caught the issue in time, the sisters' brother starts showing similar symptoms. Because Cristina is busy on this case, Shane has to step up and take care of the babies in Cristina's trial, a.k.a. her "baby." Alex receives an offer from a doctor who runs his own private practice. Alex seriously considers and starts to discuss it with Jo. April and Bailey operate on a child who is very susceptible to infection due to his condition that is no longer treatable with the enzyme treatments he was previously receiving.