Grimm´s finest fairy tales: The worn dancing shoes

It's the same story every morning: The king's twelve daughters have worn out their dancing shoes the night before. The king promises one of his daughters in marriage to whoever solves the riddle of what the princesses do every night. Each volunteer has three days time, or else they face death. But each young man that tries falls asleep without solving the puzzle. Then one day, a poor soldier with a cloak of invisibility steps forward. (official distributor synopsis)