Robert Harris’ novels dwell, for the most part, astutely and chillingly on conspiracy and corruption of power. They are at work in his great trilogy on Cicero and in his true masterpiece, “An Officer and a Spy,” about the Dreyfus Affair. He cooks them up in counterfactual speculation, as in “Archangel,” which produces Stalin’s secret son, and in “The Fear Index,” which gives us a machine-learning algorithm run amok, intent on its own lethal designs. And, indeed, it just might be that an outbreak of computer mayhem is the reason the characters in his present novel, “The Second Sleep,” are living in a future that has devolved to the technical and cultural level of the Middle Ages.

It is 1468 in the era of “Our Risen Lord,” some eight centuries on from our own time. A lone traveler is on the road heading to a village in Wessex as though he were setting out in a novel by Thomas Hardy. This is Father Fairfax, a young priest come to bury the village pastor, Father Lacy, who either fell to his death or was murdered. Fairfax lodges in the late pastor’s house and discovers that the man had been collecting artifacts from a vanished civilization. We eventually learn that this must be our own, an era which came to some unknown catastrophic end in 2025, later dubbed the year 666 in the new dispensation.

Society is now run by the Church, which considers science heresy and forbids investigations into the past and its scientific knowledge — not that they would be especially easy, as in those bygone days “an entire generation’s correspondence and memories had vanished into this mysterious entity the antiquarians called “the Cloud.”

Among the relics on display in the old priest’s study is a small rectangular object bearing the image of an apple with a bite taken out of it — you don’t have to be a biblical scholar to get the significance of that. Fired by unsanctified curiosity, Fairfax delves into the outlawed books in Lacy’s library and becomes obsessed with a certain Nobel laureate, Peter Morgenstern, who in 2022 A.D. pointed to the potential destruction of present “science-based way of life.”

Risking the disfavor of the bishop, a man called Pole (a tip of the miter to Reginald Pole, reactionary cardinal during the reign of “Bloody Mary” Tudor?), Fairfax sets out with a couple of persecuted antiquarians to an archaeological dig. Also along are a beautiful widow, her brutal mill-owner suitor, and 30 or so of his workers. What results is a jumble of violence, treachery and improbability. Though inoculated with conspiracy, the novel, Harris’ 13th, is his least diabolically savvy; the conceit upon which it is based is shopworn, while its plot, after delivering one nicely evil surprise, finally gives up and ends with a thunk.

 Katherine A. Powers, a Minnesota native, reviews for the Washington Post, the Wall Street Journal and elsewhere.

The Second Sleep
By: Robert Harris.
Publisher: Alfred A. Knopf, 298 pages, $26.95