The Hyacinth Spell — Frances Y. McHugh

A small lake village in upstate New York is the last place in the world where one would expect to find witches and warlocks, men wearing goat's heads, and human sacrifices by the light of the moon. In fact, Karen Foster had come there to rest and refresh herself, gratefully accepting her boss's offer of a visit to his place on the island of Sanctuary in Lake Tranquil. As she stepped from the bus, she took deep breaths of unpolluted air and looked around her at the calm lake waters, the mountains in the distance, and the boats gently rocking at the pier across the road. Little did she dream Sanctuary could be anything but paradise . . .