Imagine, if you will, a Pynchonesque mega-novel that periodically calls to mind the films "Inception" and "The Matrix," Raymond Chandler's quest romances about detective Philip Marlowe, John le Carré's intricately recursive "Tinker, Tailor, Soldier, Spy," the dizzying science fiction of Philip K. Dick, William Gibson and Neal Stephenson, Iain Pears's hypertextual "Arcadia" and Haruki Murakami's alternate world "IQ84" and even this week's Washington Post story about China's push for "total surveillance."

What would such an ambitious book look like? You know the answer already.

Nick Harkaway's "Gnomon" opens in the not-too-distant future, when England is governed by the System. Perfect security has been achieved through a constant monitoring of virtually all citizens. Cameras, microphones and other sensors are ubiquitous. Every aspect of a person's life is immediately gathered into a vast database. Each day a cross section of the populace votes on civic questions and proposed regulations — the polls, not the pols, guarantee a kind of pure democracy. In exchange for total personal transparency, the System offers safety and empowerment to all.

In this world, a police force, called the Witness, often prevents crimes before they happen. Through high-level technology its officers communicate nonstop with a kind of super-Siri. They can even employ instant lie detection to assess an informant's honesty and level of sincerity. In some extreme cases, surgical probes may be used in interrogation. These are widely recognized as benign, with no debilitating consequences. At least not usually.

"The death of a suspect in custody," says Inspector Neith in the opening sentence of "Gnomon," "is a very serious matter. There is no one at the Witness Programme who does not feel a sense of personal failure this morning." An ornery old woman named Diana Hunter has died during a supposedly routine interrogation, and Neith, well known for her probity, has been assigned to learn what went wrong. The case file bears the randomly generated name "Gnomon."

Gnomon? Throughout, Harkaway — not only the author of three excellent previous novels and a study of digital culture, but also, as he must be tired of hearing, the son of John le Carré — regularly drops in arcane words and literary or historical allusions, which he usually defines or identifies, though not always right away. Just keep reading. A gnomon is the perpendicular part of a sundial, the part that casts a shadow.

To understand what happened to Diana Hunter, Inspector Neith employs a standard investigative tool: She connects her own mind to a Witness interface that allows her to relive — in a kind of dream-state — what Hunter was thinking during the brain probe. It grows quickly apparent that the woman was terrified the surgical procedure would, in her own words, "hollow me out like a pumpkin and leave me with a pumpkin smile: a wide, idiot, toothless grin." Hunter also turns out to have valued privacy to a seemingly paranoid degree. She has kept her house, filled with books and art, entirely free of electronics, made it a zone into which the System could not peer.

As Neith and the reader quickly guess, Diana Hunter wasn't just a kindly old lady who lent books to the neighborhood children. In fact, she had — through some kind of special training — prepared herself to combat any cranial intrusion by guarding her inner self with four wildly different screen-narratives, each recounted by a very different protagonist. In the first, a Greek mathematical genius-turned-banker relates his financial and sexual exploits. The second focuses on Saint Augustine's cast-off mistress, now grown deeply learned in the occult and desperate to bring her dead son back to life. In the third, we follow a once-famous Ethiopian painter who comes out of retirement to design the art for a computer game created by his granddaughter. For the fourth, we grow privy to the thoughts of a far-future hive-mind called Gnomon, who seems able to travel in time.

Harkaway divides up and parcels out these four narratives over the course of Neith's investigation. Each, I should stress, is genre-novel exciting just on its own. Still, one soon notices certain repeated motifs and symbols: a descent into darkness and near-death, references to ominous Fire Judges, a computer game that resembles the society of the System, a magical place sometimes called the Chamber of Isis or Firespine, the ability to walk through walls, the eerie recurrence of the number 5. What is really going on?

As the enigmatic and androgynous figure known as Lonnrot tells Neith: "The truth is rotational; it is a pattern of responses arranged around a core. As one uncovers one answer, it vanishes away to reveal another . . . until the whole is visible at one time and is revealed to be quite different from what was suggested by the individual parts." Are Hunter's narratives really fictional? Has she planted secret information in them? Could she actually be playing her interrogators and using their brain probe for mysterious ends of her own? And, most tantalizing of all, why does Lonnrot ask, "How long ago do you think Diana Hunter's interrogation started?"

Neith believes wholeheartedly in the System, convinced that universal surveillance is a small price to pay for universal ­well-being. Still, she finds herself suspicious of the smoothly debonair Oliver Smith, who runs the innocuous-sounding agency called the Turnpike Trust. An elderly bookseller later tells her that no one can locate copies of the books published by the young Diana Hunter. Eventually, the case takes Neith to Oxford to question a celebrated professor of semiotics, then to a foreign embassy to confront an old enemy known as the Waxman. Finally, a computer whiz shows her how, in an emergency, to contact a dark-web entity called Kraken.

Despite the richness of its invention and virtuosic tricksiness, "Gnomon" is probably a bit too long. Still, it means to dazzle and it does, while also raising serious questions about identity, privacy, human rights and the just society. Like a Cedar Point roller coaster, its final chapters will leave your head spinning. But what a ride!

Michael Dirda reviews books every Thursday for The Washington Post.

On Jan. 14 at 3 p.m. Nick Harkaway will be at Politics and Prose, 5015 Connecticut Ave. NW.


By Nick Harkaway

Knopf. 704 pp. $28.95