Of course, the obvious person to use the needle on first was Margaret. He may have been more turned on by corrupting minds than looking at hot naked women, but he still preferred beauty over ugliness. With this "drug", he could enhance Margaret's breasts and make her look at least a bit younger in one portion of her body. He didn't have a way to change people's ages, to make them younger ... yet. Give him some time. He'd figure something out.
Derek walked out towards the pool area and grinned when Margaret and Samantha noticed him. They jumped up out of their chairs and beamed with delight.
Margaret nearly ran towards him and asked "Master, is it time for me to please you?"
"Yes."
Margaret giggled and clapped her hands. She was so happy.
"It would please me greatly if you let me use this needle on you."
"Ooh, what's in it? What's it do?"
"It makes your breasts bigger and incredibly firm. You want that, right?"
She smiled. "Oh, yes, Master."
Derek grinned, then administered the shot.
