What if the Miller’s daughter couldn’t give away her firstborn to Rumpelstiltskin because it was already his?
The Miller’s daughter has been cursed with powers to read people’s minds. The King wants her to give him his deepest desire, but she can’t find out what it is on her own.
Rumpelstiltskin will help the Miller’s daughter at a price. His price becomes higher as the demands of the King increase, until he asks for something he cannot have.