The Nixie of the Mill-Pond

We should be very careful with the agreements we make because do you know what happened in "The Nixie of the Mill-Pond"? A rich man made a bargain with a nixie: the nixie was going to make sure that the wealth in the family did not reach an end while in exchange it could take whatever was just born in the house. And unfortunately it was the rich man's son. He did everything he could to keep his child away from the pond where the nixie lived.
Will his fears however come true or his son's life will be spared?