There was a king who had twelve beautiful daughters. They slept in twelve beds all in one room and when they went to bed, the doors were shut and locked up. However, every morning their shoes were found to be quite worn through as if they had been danced in all night. Nobody could find out how it happened, or where the princesses had been.
So the king made it known to all the land that if any person could discover the secret and find out where it was that the princesses danced in the night, he would have the one he liked best to take as his wife, and would be king after his death. But whoever tried and did not succeed, after three days and nights, they would be put to death.