He kneels down before the King and Queen and begs for them to hear him out. He says that he can make them more gold than they could ever imagine. And the only thing condition is that they let him stay and give him free hospitality.
Giving the King his gold
Well done! I'll have someone come and test it tomorrow.
They accept his offer and give him a place to sleep and conduct his work. He fills a container with a strange fluid and drops into it three Copper coated Zinc coins
The great escape
By heating the fluid with the coins., he is able to magically turn them into silver. But he takes it one step further and heats the coins again without the fluid. He is making it look like he is making gold. When in reality he is forming brass to fool the King.
He presents the Gold he created to the King and Queen.
Your Majesty, I have your gold!
He quickly escapes from the castle in the dead of night. He was never seen again.