1Twins discover there's more then just being siblings.
1She finds sexual happiness, then loses it.
2She feels the distance is getting greater.
3Mom finally meets her rival.
Lost in the depths of a cave with a carnivorous beast.
Al and his mother learn of their feelings for each other.
Shari and Cassy team up against dad.
His desires expand to include mom.
Al's desires expand to include others besides sister.