Kivrin and Dunworthy realize that she has arrived in England in 1348 during the Black Death pandemic, more than 20 years later than intended. Because there's no slippage (the time shift between a traveler's intended and actual date of arrival, ensuring they can't change history), it's believed that Badri, delirious with illness, input the incorrect coordinates. It turns out that Badri contracted the influenza virus from human remains at the archaeological dig, when he had been helping there, starting the epidemic at future Oxford.