Admirers of Paul West's recent fiction probably won't be surprised to learn that this new novel, despite its title, begins not as a tale of crime or horror but as a quirky, almost dreamy love story—complete with a plucky shopgirl, a real-life prince and a soon-to-be-famous artist as matchmaker. After all, in such books as Lord Byron's Doctor and The Very Rich Hours of Count von Stauffenberg, Mr. West burrowed his way into history from the oddest angles, weaving in and around factual episodes (Byron and Shelley on vacation, the von Stauffenberg plot to assassinate Hitler) with nervy imagination. His specialty is filling in the missing details—psychological and otherwise—through verbally exquisite interior monologues or provocatively vivid evocations of unfamiliar milieus.

This time, of course, it isn't just the details that need fictional filling in. It's virtually the whole story, since no one has ever proved whodunit, let alone offered a convincing explanation of the motive behind the savage murders of five East End prostitutes in the autumn of 1888. Indeed, although speculations abound, the Ripper remains true crime's most enduring unsolved mystery. So there's special fascination and suspense as Mr. West's narrative, whimsically expansive yet also firmly paced, demonstrates how that illiterate shopgirl's 1884 romance supposedly led to the mayhem in Whitechapel four years later.

The smitten prince is none other than Queen Victoria's slowwitted grandson Eddy, the future Duke of Clarence, who, bored with Cambridge secretly escapes whenever possible to Cleveland Street—the Montmartre of London. The prince's guide to the bohemian life there is his surrogate older brother, the English Impressionist Walter Richard Sickert (1860–1942), then a 24-year-old "painter maudit" in the French tradition, "dabbling in all kinds of unspeakable experiences just to see what would come out at the other end in works of art." And it's Sickert who introduces Prince Eddy (a voracious bisexual) to the cheerful shopgirl-model Annie Crook, a poor Catholic lass from up north. The two far-from-innocent waifs instantly fasten upon each other with "sloppy-lipped adoration," produce a baby girl named Alice and carry on their clandestine affair over the next few years in near-perfect bliss (Eddy sometimes prefers the company at Cleveland Street's male brothel).

This idyll soon comes to an abrupt halt, however. The old Queen, having got wind of her grandson's indiscretions, wants the whole disgusting thing ended, hushed up. Her patrician Prime Minister, Lord Salisbury, afraid that a Prince Eddy scandal would fuel antimonarchist, revolutionary rumblings, couldn't agree more. He arranges for thugs to abduct Annie Crook and drag her off to Guy's Hospital, where she's lobotomized and put under permanent wraps by jovial Sir William Gull (1816–90), the personal physician to the royal family as well as "the most famous vivisectionist of his day."

Won't anyone act or speak out against such an outrage? Not Sickert: he's far too fearful (for himself and Annie's child), far too ambitious, for heroism. But Annie's best chum, a breezy, confident young prostitute named Marie Kelly (Sickert's sometime mistress), does dare to strike back. Fortified by anger and alcohol, egged on by three of her colleagues, Marie writes audacious blackmail notes to the powers that be—and all four women of Whitechapel sign the letters, which threaten a public airing of the dirty linen unless Annie is freed and the women's silence paid for. So it's not long before Sir William, the Queen's "silencer," begins touring the East End by night in a horse-drawn carriage, offering rides to a very select group of prostitutes. His highly reluctant accomplice: Walter Sickert, who can identify most of the would-be blackmailers by sight. The killings, assumed to be the random attacks of a sex-crazed maniac, are in fact death sentences carried out against enemies of the state—with no less tacit approval than Becket's murders received from Henry II.

Unfortunately, Mr. West can't be given credit for this gloriously farfetched, deeply beguiling plot. His prefatory note—acknowledging that Stephen Knight's Jack the Ripper: The Final Solution "fed me some usefully preposterous données"—doesn't suggest, perhaps, the extent to which The Women of Whitechapel and Jack the Ripper follows Knight's elaborate theory of the case. The Eddy/Annie liaison, the abduction, the blackmail attempt, the modus operandi of the killings, the roles played by Guil and Sickert and others—all these basic elements, along with a few surprising twists and dozens of details, are derived from Knight's 1976 book, which was itself largely based on interviews with Joseph Sickert, the painter's natural son, who claimed to have heard the story from his Ripper-obsessed father.

Knight's theory, like earlier speculation that Prince Eddy himself was the Ripper, has since been discredited by Donald Rumbelow and other "Ripperologists." Joseph Sickert confessed in 1978 that most of his account was "a whopping fib," although he stuck to his claim that his mother was Alice, the Prince's illegitimate daughter.

Still, whoever originated the tale, and whatever its iffy relationship to historical fact, Mr. West has generally made the most of it as fiction. The late Victorian period, with all its charm and filth and wretchedness, is delivered up in dazzling set pieces—from frolics with a bathing machine at Yarmouth to a plague of flies descending on London—that never interfere with the story's grimly steady momentum. Mr. West's lyrical, clever prose, now and then too ostentatiously paraded in his previous novels, remains under shrewd control here.

Each of the victimized prostitutes registers as a distinct, warm-blooded personality—especially the bumptious, unapologetically lewd Marie Kelly. Whether playing nanny to little Alice, hawking condoms, composing a letter to the Queen ("was it behoves or behooves?"), or fantasizing about group sex with the Prince of Wales and a whip-lashing William Gladstone, Marie commands the stage—a great character out of some alternative, X-rated Dickens—without becoming a scatological cartoon. She also emerges as a bona fide radical feminist hero of sorts, making Mr. West's sporadic attempts at explicit political statement (the exploitation of women, the sins of capitalism) seem redundant.

Sickert, the novel's central figure, is more problematic. At first his depiction as the experience-hungry artist—an "addict of the seamy," the "muse of the unsavory"—verges on mere bohemian stereotype, although Mr. West does shade in the portrait with a few fetching, idiosyncratic touches. In moments of great stress Sickert dresses up in assorted costumes; in moments of private glee he does his "Affable Arthur walk," a comical music-hall strut. Eventually, however, as events force Sickert into ever more ghastly situations, his confrontations with the evil within do take on poignant, if not quite tragic, dimensions.

Witnessing the Ripper's brutal mutilations, he finds himself "reluctantly stimulated, insufficiently repelled, secretly enthralled." The fine line between amorality and monstrosity is fiercely illuminated: "One wrong step was all it took, and down the gradient you went screaming, lapsed from being what your headmaster called A Boy of Ability Who Does Not Concentrate or Work Hard to a slobbering demon."

Throughout, in fact, no matter how literary and bawdy and ironic Mr. West's treatment of this melodramatic material may become, he continually rediscovers—and summons up fresh for us—the genuine horror in heinous deeds. No small achievement, not in these low-affect days of teen-age slasher movies, the corpse-strewn 6 O'Clock News and American Psycho.