Zenobie — Barbara Hambly

A novelette of 16,000 words. Computer programmer Joanna Sheraton's hippie mother asks the help of her daughter's partner - exiled wizard Antryg Windrose - in getting rid of a spectre which seems to be haunting the New Age Consciousness-Raising Center in Bayou Chien Mort, Louisiana. Upon arrival, Antryg and Joanna begin to suspect that there is a lot more going on than anyone is willing to admit, with results potentially more deadly than noises in the night and a little blood on the walls.