Known in Pennsylvania Dutch as Brauche or Braucherei, the folk-healing practice of powwowing was thought to draw upon the power of God to heal all manner of physical and spiritual ills. Yet some people believed--and still believe today--that this power to heal came not from God, but from the devil. Controversy over powwowing came to a climax in 1929 with the York Hex Murder Trial, in which one powwower killed another who, he believed, had placed a hex on him.

Based on seven years of fieldwork and extensive interviews, David Kriebel's study reveals the vibrant world,...