Mira Belochkin is a former lover of Pnin's. They are separated because of a war and she marries someone else later on in her life. She functions in the novel to reveal how Pnin deals (or does not) with tragedy and loss. Because she is killed in an extermination camp, Pnin cannot think of her. He rejects any memory, tortured in imagining any of her possible painful deaths there. The reader learns a lot more about Pnin in what is not said in the passage refrencing her, such as his ability to hide this important part of his life from us as well as the narrator.