In an intriguing afterword to John le Carré’s last novel, “Silverview” (2021), Nick Harkaway, the novelist’s son, wrote that he had promised to finish any work of fiction his father left incomplete at the time of his death. When le Carré died in 2020, Harkaway thought there might be quite a bit of work to do. Then he read “Silverview” and discovered that the book was “not incomplete, but withheld.” Why?

Harkaway gives us two answers. One is a theory sketched in his afterword. The other is a new novel called “Karla’s Choice,” attributed to Harkaway but also billed as “a John le Carré novel.”

The theory is that “Silverview,” in which a bookseller befriends a retired agent of the British secret intelligence service and learns more than he wants to know about hidden knowledge and changing loyalties, does “something that no other le Carré novel ever has. It shows a service fragmented … and ultimately not sure, any more, that it can justify itself.”

Harkaway thinks his father, a former intelligence officer, “couldn’t quite bring himself to say that out loud. … He wrote a wonderful book, but when he looked at it, he found it cut too close to the bone.”

It’s a good theory. In “Silverview,” a senior member of the service describes what a “misguided” writer has been highlighting as the current politics of western espionage:

All pretty much as one would suppose … America’s determination to manage the Middle East at all costs, its habit of launching a new war every time it needs to deal with the effects of the last one it launched. NATO as a leftover Cold War relic doing more harm than good. And poor, toothless, leaderless Britain tagging along behind because it still dreams of greatness and doesn’t know what else to dream about.

There is no indication that the speaker agrees with these propositions. No indication that he doesn’t either.

“Karla’s Choice” confirms the theory but it also refines it, and suggests different ways of saying things out loud. In an author’s note, Harkaway tells us he was hoping to “fit some sort of story into that 10-year gap” between le Carré’s breakout novel, “The Spy Who Came in From the Cold” (1963), and “Tinker Tailor Soldier Spy” (1974). He does this very precisely.

George Smiley, le Carré’s best-known character, returns from retirement; he wants to think temporarily, “as a consulting ex-spy rather than a full-time member” of the service, or the Circus, as it’s known in the novels. The story line concerns Susanna, a Hungarian woman living so close to the secret world in London that she finally joins it. Her boss is a literary agent who turns out to be a misbehaving Soviet operative named Ferencz Róka. He has disappeared, and much of the novel shows us in detail how the collected officers of the Circus reconstruct his life and goals.

In a memorable phrase, Smiley tells his chief that “although we know what Róka wants, we have no idea where he is.” This is what needs to be remedied.

Smiley and some colleagues (and Susanna) take off for Berlin and Vienna to see what they can find. They need to know what Róka knows, not just what he wants, and they wouldn’t mind saving his life if possible.

The year is 1963, two years after the construction of the Berlin Wall, where, in an earlier novel, the British agent Alec Leamas and a woman called Liz Gold are killed as they attempt to escape to the West. “Karla’s Choice” is full of the memory of this event, and it often feels as if Smiley’s central project is to avoid the occurrence of anything resembling it: spying not without cost but without terminal cancellation. “When Alec Leamas’s ghost was at his shoulder,” Harkaway writes, “he wanted above all to show that the brutal passages of his recent life were an aberration and not his underlying truth.”

We may wonder whether Harkaway wants to make him sound quite so hopeless and deluded. We wonder again when a character says of Smiley that “he believes in the West,” and another announces that “Smiley believed not in ideology but — against the evidence — in people.”

One of Harkaway’s more subtle moves is to insist on similes of blur and sogginess: “as if a fog were paying attention to the house it surrounded”; “when the fog of espionage covered the field.”

Le Carré wrote in 2012 that “The Spy Who Came in From the Cold” “was the work of a wayward imagination brought to the end of its tether by political disgust and personal confusion.” He reminds us that “to the hard-liners of East and West the Second World War was a distraction.” Thinking of Kim Philby, the British double agent revealed in 1963 as “Moscow’s man,” le Carré writes of “a state of corporate rot that would take another generation to heal.”

Le Carré, whose own career as a spy is said to have ended because Philby blew his cover, then asks whether his character Alec Leamas knew about the decline of “the service that owned his unflinching allegiance,” and answers, “I think deep down he did.”

He adds: “And I think I must have known it too.”