A young girl who is almost 18 has been wanting to have a sexual relationship with her father is getting frustrated with being unable to approach her father about the subject. Strangely though she's able to talk to her Step-Mother about it. The Step-Mom tells the girl that she could talk her husband into having sex with her. But first the girl needs to give the Step-Mom's son a sibling. That is when the Step-Mom tells the story that she had been having sex with her husband's father since she was a teenager. And the father of her son is in fact the girl's Grandfather. Not even her husband knows that fact. She tells the girl that she'd love sex with her grandfather, that he is a really great lover. Eventually the girl agrees to having sex with her grandfather and having his baby. After the baby is born and she's able to have sex again her step-mother comes through on her end of the promise. The girl has sex with her father and gets impregnated by him.