On December 1, 1934, Sergei Kirov, the head of the Communist Party in Leningrad, was shot and killed in the hallway outside his office. The assassin, an unemployed man who had been expelled from the Party and bore a grudge against its leadership, was apprehended on the spot, but the case still raised questions. How did the killer get his pistol? Who had called off the bodyguards who usually surrounded Kirov at all times?

Today, most historians agree that it was Joseph Stalin himself who ordered the murder, in order to eliminate a potential rival. But the official investigation came to quite different conclusions. During the next four years, it metastasized into a conspiracy-hunt that claimed to expose shocking villainy at the highest levels of Russia’s government, military, and industry. In a series of trials that were publicized around the world, some of the oldest and most trusted Bolshevik leaders—men who, with Lenin, had led the Russian Revolution—were accused of being traitors. Supposedly, acting on orders from Stalin’s exiled rival Leon Trotsky, they had plotted to murder Stalin, to hand Soviet territory over to Nazi Germany, and to restore capitalism in Russia. Their alleged methods included not just assassinations but also industrial sabotage, or “wrecking”—even putting ground glass in the nation’s butter supply.

At the conclusion of the trial of two veteran Party leaders, Lev Kamenev and Grigory Zinoviev, the state prosecutor general, Andrey Vyshinsky, denounced the defendants with florid Stalinist rhetoric: “These mad dogs of capitalism tried to tear limb from limb the best of the best of our Soviet land. . . . I demand that these dogs gone mad should be shot—every one of them!” There was never any doubt about the verdict or the sentence. And the Party leaders who were condemned, in what came to be known as the Moscow Trials, were only the most prominent of the victims. Stalin’s Great Purge, of 1936-38, ultimately took the lives of a million Soviet citizens, and sent millions more to the Gulag.

By the late nineteen-thirties, Western intellectuals who sympathized with Communism had already proved themselves capable of accepting a great deal of killing in the name of the cause. Such “fellow-travellers” usually justified Stalinism’s crimes as the necessary price of building a socialist future, and of defending it against a hostile capitalist world. Walter Duranty, the Times’ correspondent in Moscow, excused the three million famine deaths that were caused by the push to collectivize Soviet agriculture, writing that, “to put it brutally—you can’t make an omelet without breaking eggs.”

The Moscow Trials, however, presented a different sort of challenge to the Communist faith. It was one thing to unleash the power of the state against kulaks, the wealthy peasants who were key villains in Soviet mythology. But how could it be that Old Bolsheviks, who had, until the day before yesterday, been the rulers of the Soviet Union, were secret counter-revolutionaries? On the other hand, if the charges were false, why did the defendants confess? Zinoviev, who had been a member of the first Politburo, in 1917, and the head of the Comintern, said, “My defective Bolshevism became transformed into anti-Bolshevism, and through Trotskyism I arrived at Fascism.” Kamenev concluded his statement by addressing his children: “No matter what my sentence will be, I in advance consider it just. Don’t look back. Go forward together with the Soviet people, follow Stalin.”

Did such men simply give in to prolonged interrogation—the so-called “conveyor,” whereby prisoners were questioned for days on end by a team of agents working in shifts—or to outright torture? Were they trying to protect their wives and children, who were effectively Stalin’s hostages? Or did they feel that, in some obscure way, they deserved punishment for crimes they hadn’t committed? Here was a problem for a psychologist—or, better, for a novelist, one who understood Communism from the inside and knew what it was like to be a political prisoner.

That novelist was Arthur Koestler, and the book that the Moscow Trials inspired him to write was “Darkness at Noon,” which became one of the most important political novels of the twentieth century. Telling the story of a veteran Bolshevik who is awaiting trial for treason, the book originally appeared in December, 1940, just two years after the events that it drew on, and became a worldwide phenomenon. In America, it was a best-seller and a Book-of-the-Month Club selection, and was soon adapted into a hit Broadway play. When it appeared in France, in the spring of 1945, it sold half a million copies. Some observers credited “Darkness at Noon” with tipping the balance against the Communists in the French elections of 1946.

Now Scribner has published a new translation of the book, by Philip Boehm, based on the original German manuscript, which was discovered in a Swiss archive in 2015 after being lost for seventy-five years. The story of how it disappeared in the first place gives a vivid sense of the dislocated world from which the novel emerged. Koestler began writing “Darkness at Noon”—under its original title, “The Vicious Circle”—early in 1939, in France, where he had lived as a stateless refugee ever since Hitler came to power in Germany, six years before. When the Second World War broke out, that September, the French government took the opportunity to sweep up such immigrants—especially those who, like Koestler, had Communist Party connections—and put them in internment camps.

From October, 1939, to January, 1940, Koestler had to abandon work on the novel while he was a prisoner at a camp in southwestern France. When he was released, after string-pulling by some highly placed literary and political friends, he returned to Paris and quickly finished the book. As Koestler worked, his English girlfriend, Daphne Hardy, sat in the same room producing an English translation, and, at the beginning of May, both manuscripts were mailed out—the English version to a publisher in London, and the German version to a publisher in neutral Switzerland.

Ten days later, the Germans invaded France and swiftly conquered the country. Koestler, who was a Jew, a Communist, and a refugee, knew that if he fell into Nazi hands he would certainly be killed, and he and Hardy embarked on a headlong dash for the unoccupied southern zone of the country, separating along the way. Hardy, a British citizen, made it back to London fairly easily, but Koestler underwent a months-long odyssey, during which he joined and then quit the French Foreign Legion, twice attempted suicide (once with morphine, once with cyanide—miraculously, neither worked), and finally smuggled himself, via Morocco and Portugal, to England, where he was promptly arrested once again.

While he was in transit, Hardy had been corresponding with the London publisher, which, despite some reservations, had accepted the novel for publication. When the publisher objected to Koestler’s original title, it was Hardy who, unable to contact Koestler, decided on calling it “Darkness at Noon.” The phrase was an allusion to Job 5:14: “They meet with darkness in the daytime, and grope in the noonday as in the night”—a description of both the moral conundrums facing the novel’s protagonist and the desperate plight of Koestler himself. The German manuscript, meanwhile, was presumed to have been lost in the chaos of war, and so the English translation of the novel became, in effect, the original, from which all subsequent translations were made, including one back into German. The new edition is the first to return to Koestler’s German text, and aims to replace Hardy’s version, which was the hasty work of an inexperienced translator—though, clearly, it was good enough to have secured the novel’s global reputation.