Potter, a moment of your time, please.

Someone has been stealing ingredients that could be used to make polyjuice potions.

I know, I know. "It wasn't me professor, I would never transform into a girl and masturbate to find out how it feels", I've heard this little song and dance before.

When I was your age I was the same. Did I ever tell you I stole your mother's hair regularly? I became quite adept at stealth and potions for this precise reason. To transform into your mother and pleasure myself.

There is this mirror... or there was, at any rate, I can't seem to find it anymore, that showed you your fondest wish. I would transform into your mother, look into that mirror and watch myself make love to her while your father watched, helpless to change anything

Those were the best orgasms of my life, Potter. One day things went wrong,

Before I could find my way to a safe spot, your father found me, and thinking me Lily proceeded to fondle me

It felt good, Potter. Forbidden fruit tastes the sweetest

You know that polyjuice potion doesn't change your voice, of course. Yet James Potter never suspected a thing when I didn't speak. He smiled and said I was learning.

Oh I learned alright. I learned never to touch polyjuice potion again. Not because I feared such a thing would happen again, but because I feared I would want it to. That I'd seek it out.

Polyjuice potion and it's ingredients are restricted for a reason, Potter. The very recipe is not available to students.

Keep that in mind, won't you?