This story is A Weekend to Remember, in which a woman turns fantasy into incestuous reality, retold from the perspective of the woman’s 14-year-old nephew. All the actual quoted speech is exactly the same in both versions, but the dialog attributions, the descriptions of the activities, and the internal thoughts of the narrator have been changed to reflect the different viewpoint.
A dark and mysterious woman has an insatiable sexual appetite and a rather large surprise in her pants. A (fortunate?) young man becomes her latest obsession and prolific debauchery ensues.
June goes out for a morning run, when a storm comes upon her. She makes it to her garage safely, bringing in a young girl going to school with her, upon which an erotic workout ensues.