The Silver Curlew — Eleanor Farjeon

The Silver Curlew is one of Eleanor Farjeon's finest works, an intriguing re-telling of the classic story Rumpelstiltskin. Mother Codling lives with her children in a small, Norfolk windmill. One day, the Codlngs receive a surprise visit from the king of Norwich, who insists that eighteen-year-old Doll Codling must spin a certain amount of flax for him, or he will cut off her head.
Doll, terrified of dying, makes a deal with a spindle-imp, in order to save herself and her family. The only clincher is, that he returns to the castle when Doll's daughter is born and insists that he take the newborn child as payment for his work.
Doll, and her younger sister Poll, try desperately to keep the baby...