Every intelligent grandmother knows that the fire must not be allowed to go out in a room where there is a child not yet christened; that the water in which the newborn child is washed should not be thrown out; also, that a needle, or some other article of steel must be attached to its bandages [diapers]. If attention is not paid to these precautions it may happen that the child will be exchanged by the trolls, as once occurred in Bettna many years ago.
A young peasant's wife had given birth to her first child. Her mother, who lived some distance away, was on hand to officiate in the first duties attending its coming, but the evening before the day on which the child should be christened she was obliged to go home for a short time to attend to the wants of her own family, and during her absence the fire was allowed to go out.
No one would have noticed anything unusual, perhaps, if the child had not, during the baptism, cried like a fiend. After some weeks, however, the parents began to observe a change. It became ugly, cried continuously, and was so greedy that it devoured everything that came in its way. The people being poor, they were in great danger of being eaten out of house and home. There could no longer be any doubt that the child was a changeling. Whereupon the husband sought a wise old woman, who, it was said, could instruct the parents what to do to get back their own child.
The mother was directed to build a fire in the bake oven three Thursday evenings in succession, lay the young one upon the bake shovel, then pretend that she was about to throw it into the fire. The advice was followed, and when the woman, the third evening, was in the act of throwing the changeling into the fire, it seemed, a little deformed, evil-eyed woman rushed up with the natural child, threw it in the crib, and requested the return of her child.
"For," said she, "I have never treated your child so badly and I have never thought to do it such harm as you now propose doing mine," whereupon she took the unnatural child and vanished through the door.
Swedish folk tale