The Twelve Dancing Princesses
The Best of the Brothers Grimm

There was once a king who had twelve beautiful daughters. Every night the king locked the door to their bedroom but at some point the twelve princesses would sneak out and dance the night away. The king desperately wanted to know where the princesses danced but it remained their secret.In an effort to find the answer to this riddle the king proclaimed that whoever would accept the challenge of discovering their secret would marry the princess of his choice. If, however, if anyone accepted the challenge and failed to discover the secret he would be killed.Many tried and failed until one young man out-smarted the princesses and discovered where they danced. He married on of the princesses and became the heir to the kingdom.