In the wake of the Black Plague and the Church schism between Rome and Avignon, the late 14th century was a convulsion in the spirit of western man. The plague cut huge swaths through the population of Europe, shattering the feudal structure, starving the poor and paupering the rich. Human response was to grovel even lower before the cross while wondering just what power it was that truly ruled over such chaos. In 1387, with men's faces still scarred from the pox, life was as terrible as the day after World War III.

"A Mortal Glamour" is dark fantasy, but one woven whole-cloth from the human mind: the horror and spiritual agony endured by nuns of the Convent of la Tre s Saunte Annunciacion near Avignon. Not all the nuns of the convent have a true vocation. Lusty young Seur Aungelique has been forced to the veil because her family needs Church favor and refuses her desired marriage to a young duke, Pierre Fornault. Seur Philomine is much the same. Wit-wandering Seur Marguerite, the hive-keeper, sings and prays to her bees, Seur Catant is an epileptic, only a blink away from hysteria.

When the new young superior, Me re Le'onie, assumes command of the convent, she sets about with chill severity to correct what she deems the sloth and error of the past. Vigils and fasting push the women, already in fear of fanatical Flagellants roaming the roads, to a neurotic edge. The central forces of this bleak story are not immediately apparent, nor is any one protagonist good or evil. Nevertheless they begin to draw together, clearer and clearer. Over them all looms the shadow of the cold war between Avignon and Rome.

Me re Le'onie and the nuns defend the convent against attacking Flagellants whose approach to their walls is one of the scariest moments in the book. When Fornault comes to the sisters' aid, it is apparent that they have closed as much evil within the walls as they have repelled.

Aungelique and others have erotic visitations in the night that they don't want to deny, waking the other women with the sound of their ecstasy. The bees die; food goes bad. Pe re Guibert, the convent's confessor, knows that the devil has entered the convent. Indeed, he has chatted with addled Seur Marguerite at her prayers, even impregnated Aungelique and Seur Ranegonde. A simple man with a pathetic secret of his own, Guibert informs Avignon. The bishop sends an inquisitor, Eve que Amalrie, to interrogate the nuns with brutal scourgings. Gradually the House of God becomes a suburb of hell, and through it all stalks the incubus figure of sensual Thibault Col, appearing at will to whatever women he pleases; just as ubiquitous is the steely presence of Me re Le'onie.

There is no single tragedy to "A Mortal Glamour," but the arrangement on a dark stage of individuals, each a fact of the inevitable end. When it falls, even the courageous Pierre Fornault is too numb and helpless to do more than stammer his guilt and offer himself to the rack. While cool Me re Le'onie meditates in her cell, Thibault Col unerringly brings to each of them, man and woman, what they most fear and most desire. The end goes beyond irony and tragedy to a cold existential truth. This is a grim, unsettling novel that mirrors the fear-filled adolescence of the western mind and the suppressed place of women within it.

There is a cold rage in Yarbro's work. She portrays brutalized women without grinding an ax and clearly knows much more of her subject than she feels compelled to weight into her text. Yarbro brings the economy of her fine short-story technique to this novel: There is no scene without an organic purpose. Subtlety there is, especially in the marvelous ambiguities of Me re Le'onie and Thibault Col, but now and then Yarbro's dialogue falls to heavy breathing, mostly through a minor but irritating choice. No one can voice a simple thought without hesitation or get from subject to verb without dot-dot-dot between them. The pages are awash with ellipses, a needlessly distracting fault of ear rather than sense, like the constant obtrusion of a stage mannerism, that should have been toned down in an otherwise fine, harrowing book.