The hospital gets inundated with flu infected patients, which causes the doctors to slowly fall ill one by one. Derek must fight off the sickness as he prepares to give a speech on brain mapping and the residents place bets on who will fall ill first. Meanwhile, a new doctor at the hospital gives Alex a glimpse into an alternate form of medical practice.

Cristina won't let herself get excited when she is nominated for a Harper Avery award; Alex thinks about making a change; Callie and Derek work with a machine that recognizes emotions.

Cristina enlists Meredith to help her prepare an acceptance speech for her possible Harper Avery win and while Owen offers to attend the ceremony with her, she insists on going alone. Meanwhile, Derek feels overwhelmed between his responsibilities at home and at the hospital. April and Jackson come to a disagreement on children and religion, and Callie and Arizona try to reconnect in their marriage.

Jackson is given the daunting task of delivering disappointing news to the doctors. Meanwhile, Derek's sister Amelia drops by for a surprise visit, Richard surprises Catherine in Boston and when Bailey gets frustrated by the slow pace of her research, she makes a risky decision.

Cristina considers her future at the hospital; Amelia and Derek collaborate on a tough surgery involving conjoined twins; Jo takes on too many cases at once; Stephanie stumbles on the truth about Bailey's case.

The doctors of Grey Sloan Memorial Hospital bid an emotional farewell to the beloved Cristina Yang. A possible act of terrorism rocks Seattle and causes chaos at the hospital. Meanwhile, Meredith makes a life changing decision and one doctor receives shocking news.

Maggie tries to make a good impression but finds herself in unfortunate situations; Richard keeps hiding his secret.