Lucy Barton, a writer, spends late October of 2019 traveling to promote her new book. She is scheduled to go to Italy and Germany in March, 2020, but in December, for no reason that she can point to, she cancels that part of the book tour. As March approaches, someone points out that she is lucky she canceled because they are having “that virus” in Italy. She doesn’t think it will come to New York, but her ex-husband, William Gerhardt, believes differently.

Early in March, William, a parasitologist, asks their daughters, both of whom live in Brooklyn, to leave the city. Their daughter Chrissy and her husband move into William’s parents’ house in Connecticut, but Becka stays in Brooklyn with her husband, Trey. When William explains what he has done to Lucy, she is confused, not understanding the danger of the impending situation.

To convince her of the urgency, he tells her about a friend who contracted the virus and is on a ventilator, but she still does not understand. The next day, William tells her that the friend has died, and asks her to leave New York with him for a few weeks. She agrees, although she still thinks he is overreacting.