Testing with Jacob

What David had invented was a Body Alteration Device, or BAD for short.
Though he quickly realized that he could not demonstrate it in front of his wife of daughters. No, the only person he could really test it with was his equally perverted son, Jacob.

"Jacob?" David said a few minutes later as he was knocking at his son's door.
"Yeah Dad? What is it?" he heard Jacob's heavily breathing voice from inside.
Heavens! Is he masturbating? David pondered.