Stella, as we walk, is more Stella all the time. The longer I spend with her, the more I know her, the less I remember whether she is different from the old Stella. My knowledge of her inscribes itself on my memory, rolling itself back into the past and changing my recollection of it. As we walk we share things, moments we have experienced before—or which I now remember experiencing, even if three days ago I wouldn’t have.