Frothi, king of the Northland, owned some magic millstones. Other millstones grind corn, but these would grind out whatever the owner wished, if he knew how to move them. Frothi tried and tried, but they would not stir.
 
"Oh, if I could only move the millstones," he cried, "I would grind out so many good things for my people. They should all be happy and rich."
 
One day King Frothi was told that two strange women were begging at the gate to see him.
 
"Let them come in," he said, and the were brought before him.
"We have come from a land that is far away," they said.
 
"What can I do for you?" asked the king.
 
"We have come to do something for you," answered the women.
 
"There is only one thing that I wish for," said the king, "and that is to make the magic millstones grind, but you cannot do that."
 
"Why not?" asked the women. "That is just what we have come to do. That is why we stood at your gate and begged to speak to you."
 
Then the king was a happy man indeed. "Bring in the millstones," he called. "Quick, quick! Do not wait." The millstones were brought in, and the women asked, "What shall we grind for you?"
 
"Grind gold and happiness and rest for my people," cried the king gladly.
 
The women touched the magic millstones, and how they did grind! "Gold and happiness and rest for the people," said the women to one another. "Those are good wishes."
The gold was so bright and yellow that King Frothi could not bear to let it go out of his sight. "Grind more," he said to the women. "Grind faster. Why did you come to my gate if you did not wish to grind?"
 
"We are so weary," said the women. "Will you not let us rest?"
 
"You may rest for as long a time as it needs to say 'Frothi,'" cried the king, "and no longer. Now you have rested. Grind away. No one should be weary who is grinding out yellow gold."
 
"He is a wicked king," said the women. "We will grind for him no more. Mill, grind out hundreds and hundreds of strong warriors to fight Frothi and punish him for his cruel words."
 
The millstones ground faster and faster. Hundreds of warriors sprang out, and they killed Frothi and all his men.
 
"Now I shall be king," cried the strongest of the warriors. He put the two women and the magic millstones on a ship to go to a far-away land. "Grind, grind," he called to the women.
 
"But we are so weary. Please let us rest," they begged.
 
"Rest? No. Grind on, grind on. Grind salt, if you can grind nothing else."
 
Night came and the weary women were still grinding. "Will you not let us rest?" they asked.
 
"No," cried the cruel warrior. "Keep grinding, even if the ship goes to the bottom of the sea." The women ground, and it was not long before the ship really did go to the bottom, and carried the cruel warrior with it. There at the bottom of the sea are the two millstones still grinding salt, for there is no one to say that they must grind no longer. That is why the sea is salt.