Some stories are too wonderful — too filled with wonders — to set in the  present. They can’t really be called historical fiction because they  don’t serve history so much as plunder it to invent what might have  been. Such is the case with “Pure,” by Andrew Miller, a novel set during  the Age of Enlightenment that pays homage not to the dawn of reason but  to its witching hour, teeming with all that reason mocks — hobgoblins,  specters and whatever else might be lurking in the dark. A novel of  ideas disguised as a ghost story, voluptuously atmospheric, “Pure”  exerts a sensual hold over the reader.        
 It is 1785. France is on the brink of revolution, with monarchy, like  other outdated conceits, about to be swept away. Jean-Baptiste Baratte,  ambitious and forward thinking, “a disciple of Voltaire,” dreams of  building utopias where “all that offended” him can be “made good in the  imagination,” and the church and its superstitions will be replaced by  schools run by men like himself, “benign and educated.” An engineer with  experience in mining, Baratte considers himself fortunate when he is  awarded what he expects will be an enviable government commission. But  what is it, exactly, that the unnamed minister working within the  mirror-walled palace of Versailles wants him to do?        
 “At what point do you think they started to outnumber us?” the minister  asks, slow to explain the job at hand. “Who, my lord?” Baratte replies.  The answer is, of course, the dead, who are bursting the seams of Les  Innocents, the cemetery that “has been swallowing the corpses of Paris  for longer than anyone can remember,” its charnel pits having reputedly  received 50,000 corpses during a single month of the bubonic plague.         
 Now a subterranean wall separating the necropolis from the city of the  living has collapsed, and an effluvium of putrefaction is penetrating  the dwellings around the cemetery, extinguishing candles, tainting food  and even precipitating “moral disturbances, particularly among the  young.” For the author’s purposes, cleaning up the mess is a metaphor  grand enough to accommodate an existential battle between dark and  light, outmoded and enlightened, decay and purity. And though it’s  hardly the stuff of Baratte’s fantasies, “to sweep away . . . the  poisonous influence of the past” is an assignment a modern-minded  engineer can undertake with pride. “Use fire,” the not-so-modern  minister suggests to Baratte, “use brimstone.”        
 The directive turns out to be more pragmatic than fanciful. Baratte’s  first tour of Les Innocents reveals that the cemetery’s church, a place  of “permanent twilight” where the “darkness has gathered in drifts,” is  rotting from the inside out. Abandoned by its parishioners, the  structure continues to shelter a peculiar cast of misfits: a sexton and  his blooming fairy-tale rose of a granddaughter planted among the  tombstones and somehow immune to the toxic emanations that cause others  to faint; Armand, an organist who plays to the empty sanctuary; and Père  Colbert, an old priest with a “murderous temper,” whose vision has been  dimmed by a brush with “the Adversary.” Upon meeting them, Baratte  understands that “it will be the living as much as the dead he will have  to contend with.”        
 To open the graves, clear out the past and make way for the future will  require a year of Baratte’s life. He employs a crew of 30 miners to  accomplish the task and asks his old friend Lecoeur, the “fellow  philosopher” with whom he worked in the mines, to oversee the  excavation. Excited by the opportunity, like Baratte, Lecoeur has no  idea what it will cost him to force Les Innocents to disgorge what seems  an endless stream of corpses. While two females emerge as intact as  sleeping vampires, most are reduced to unarticulated bones, destined to  be stacked like kindling on horse-drawn tumbrels and removed under cover  of night, lest the spectacle disturb the locals.        
 As for Baratte, the work of exiling the dead will cost him the self he  values. Or perhaps it was merely the one to which he aspired. Why else  would he need, at bedtime, to recite “a catechism of selfhood” that  affirms his name, place of birth and career, as well as his belief in  “the power of reason”? The engineer will sustain a serious blow to his  head — yes, it’s that obvious — before he understands that the  appointment he felt lucky to get has contaminated all his high-minded  ideals, as it has the food and the air.        
 That’s just as well. Stories in which idealism smothers the attractions  of corruption aren’t much fun. Were he in his right mind, Baratte would  never fall prey to anything so radically à la mode as a suit of  pistachio green silk, for which he trades the sensible brown jacket he  inherited from his dead father, as well as a good amount of the money  entrusted to him for the completion of the project. He wouldn’t find  himself drawn to the organist, Armand, who enlists him in a band of  merry vandals intent on defacing government notices with obscenities  about the queen. He might not turn down the fast ripening charms of a  cultured young woman for the company of a notorious whore.        
 A riptide of madness is but one of the dangers of descending into the  underworld, a journey from which some will never return. For as long as  it takes to empty Les Innocents, Baratte rents a room in a house on the  perimeter of the cemetery and takes his meals with the owners, the  Monnards, and their increasingly disturbed daughter, the beautiful  Ziguette, whose breath stinks of the grave. While the corpse bride’s  parents connive to wring a proposal out of Baratte, Ziguette, who  opposes the destruction of Les Innocents “as if she felt the shovels on  her own skin,” plots something far more sinister.        
 Soon unable to sleep without a sedative, unnerved by a peculiar  scratching at his door, Baratte keeps vigil at his bedroom window,  staring down at the graveyard and the miners as they huddle around the  fires they have built among the graves. Shadows play, things lurk and  scuttle. Tobacco to combat the stench; the anesthesia of alcohol; the  company of prostitutes: how long can the miners be distracted as they go  about their hideous task? Baratte discovers that his vision of the  future is threatened less by ignorance than by his fellow man’s  ineradicable lust for violence and mayhem. “Reason, coherence, these  seem suddenly finite assets he might, this morning, tonight, next week,  abruptly come to the end of.”        
 If “Pure” has a flaw, it’s that once the novel’s insistent metaphors  begin to accumulate, from the mirrored halls of the court of the Sun  King to the wolf-like creature prowling the charnel pits, they push an  otherwise subtle narrative toward something a little too close to  allegory. But Miller’s gift for characterization and ability to summon  up a world that convinces absolutely, even though it never was, cut  against the overt symbolism enough to excuse a flaw or two — especially  as the irrational and occult whittle away at “the power of reason.”  Heavens, if everyone behaved reasonably, novels might not exist at all.         
Kathryn Harrison’s most recent novel, “Enchantments,” was published in March.