He points at you and shouts "regress" and a cloud of smoke appears around you.
When it clears, everything is a lot bigger, and your clothes are barely hanging off of you. You quickly look yourself over, and you come to the conclusion you're only abouy three years old. You try to run at the man, hoping to knock the books out of his hands, but you just trip on your oversized clothing, and end up sprawled on the ground naked.
"I don't think you'll be much of a problem now. What can you do? If you go tell anyone they'll just think you're making up stories. If you try to follow me, well, think how a fight between a grown man and a three year old would turn out. You've lost. But, you'll still get to live, and you can even grow up and become an adult again. However, by then it'll be to late for you to stop my master's plan."
With that the man turns to leave. He's just going to leave you here as a naked toddler and do nothing!
"If I were you." The man replied. "I'd look for the nearest orphanage. At least then you would have a place to stay."
And with that he leaves.