With a slight gasp, he started to shut the door only to notice that Dad had seen him and, though slightly startled, gave Billy a wink and a knowing smile.
Bewildered, Billy retreated to his room to make sense of what he had seen.
The next day, Dad walked down the hallway and stopped at Billy's bedroom door and heard muffled sounds not unlike those made the night before in his own room. At once curious and repulsed, Dad flung the door open to see Grandma on the bed prone and Billy banging the shit out of her withered ass.
"What the fuck is going on here?!" he yelled in horror.
Billy slowly turned his head and, with a knowing smile, said "Not so funny when it's your mom, is it?"
I am so sorry about this post. No, really.