“Blithe Spirit,” the third show of the Piedmont College 2013-2014 season, is a supernatural comedy classic. After a “spirited” seance goes decidedly wrong, the cantankerous novelist Charles Condomine suddenly finds himself face-to-face with the ghost of his deceased wife, Elvira ... much to the chagrin of his current spouse, Ruth. Love and marriage devolve into laughter and mayhem when Ruth is accidentally killed and united with Elvira on the “other side.”