L. DeBard, an up-and-coming writer and an Olympic swimmer, agrees to be a coach for Aliette Huber, a New York heiress who is losing the use of her legs due to polio. The two fall in love as WWI and the Spanish flu circle their private world. Le. Debard moves into Aliette's father's mansion, ostensibly to help her train. As world affairs worsen, the Hubers quarantine behind sealed windows, order groceries on the telephone and bake the mail in the oven before opening it. They wear masks inside, but death grows all around them.

Aliette becomes pregnant and sneaks away with L. to have the child in secret. Ultimately, Aliette gets very sick and has to return to her father for better care. The father, distraught, kidnaps L. DeBard and cuts off his legs. Aliette is forbidden from ever seeing her child. 

The two never meet again, pine for each other quietly, and spend the rest of their time in penance. The plague burns itself out. L. keeps up with Aliette's swimming in the newspapers, and she reads each of his new books. Their lives run close in parallel but never touch.