In her old age, the protagonist remembers the miserable holiday in her youth when her sister fell ill with poliomyelitis. She ponders adulthood and responsibilities at her grown daughter's party as she recalls how she failed to stop the train they needed to catch to the hospital.
Cynthia didn't want children because she dislikes the imperfect. She resented her intellectually disabled brother, Philip, when they were children, and was glad when he died.
Her husband, Michael, wanted children. In the meantime, he doted on a cat, Lena, that visited their garden frequently. When Lena has an accident that injures one eye, Cynthia tries to have her euthanised; Michael stops her, but Cynthia forever hates Lena afterwards.
When Cynthia becomes pregnant, she becomes afraid that Lena will cast a curse on her baby so that it is 'imperfect'. She kills Lena - but in Lena's last moments, Cynthia regrets it, and knows she will love her baby no matter what.
