Complex sentence: Soon after occupying the house, four of the Wilber children had died over the course of seven days at the height of a local diphtheria epidemic, and the seances that were performed were usually incantations and spirit-tapping of young children.
Split into simpler sentences: Soon after occupying the house, four of the Wilber children died over the course of seven days at the height of a local diphtheria epidemic. The seances that were performed were usually incantations and spirit tapping of young children.