In March 1848 two young sisters named Kate and Margaret Fox began hearing mysterious rapping noises in their house near Rochester, New York. Interpreting thesounds as communications from the dead, the girls set up a code system by which the spirits could respond to their questions. Friends and neighbors flocked to the Fox house to ask their own questions and speak to deceased loved ones. The following year an older sister became the girls' publicity manager; P. T. Barnum made them part of his show; and they were soon national celebrities. As their fame spread, so did the national enthusiasm for Spiritualism, the belief in ommunication between living humans and disembodied spirits, generally through a medium. At seances across the country objects moved by themselves; instruments played in locked cabinets; and men and women revealed apparently unknowable information while in trance states, convincing thousands of the reality of...