Okay, so, here's what I'm thinking.
{Sigh.}
{"All right. I had hoped it wouldn't come to this, but I know your curious nature, your thirst for knowledge, will likely never let it go otherwise.}
{Look Mary straight in the eyes with a very stern expression.}
{"I can fix this glass. However, what you are about to see and learn is something that [i]must[/i] be kept top secret. I do not give this knowledge out lightly, and were it up to me, I would never have to tell anyone. I will do this only after you promise to never tell a soul what you see here. Not your kappa students, not your little magic club, not even your other half in the privacy of your house. Absolutely no one. If you break this promise, I [i]will[/i] find out. Do I make myself clear?"}