The jinn put the Mebeddel in the human baby's place. The Mebeddel slowly weakens becoming emaciated, wizened and eventually dies, making the mother think her own child has died. If the mother finds out about the switch, she can get her own child back by taking the Mebeddel to the graveyard and placing it on a broken tomb with an offering, then leaving. If she waits outside the graveyard, she'll hear her own child crying and can go back for it. Blessing it with holy water when she gets home keep the jinn from stealing it away again.