Alan Furst's Taut Tale Of WWII Espionage NIGHT SOLDIERS By Alan Furst Houghton Mifflin. 437 pp. $19.95

Face it -- what true connoisseurs of the espionage novel value most is realism. That is what the best of John le Carre', Charles McCarry and W.T. Tyler offer. No clever props, no superfluous violence. Just good writing and believable situations; and when the traitor is himself betrayed, let it be with the emotional and physical impact of an ice pick through the heart.

Consider now Alan Furst, previously thought of as a mystery writer. In "Night Soldiers," his ambitious fourth novel, he captures with exceptional fidelity and remarkable descriptive powers the shifting political and national loyalties that marked European life in the decade leading up to and including World War II. He pits the NKVD, the Soviet intelligence service, against the Gestapo, Spanish Loyalists against Nationalists, the Underground against Germans, the OSS against the NKVD, and a secret Polish nationalist organization against all comers. At novel's end, Israeli intelligence is looming.

Furst's hero is that literary rarity, a Bulgarian. The novel begins one soft autumn evening in 1934 when Khristo Stoianev, son of a Danube River fisherman, witnesses the kicking to death of his brother by some posturing fascist thugs. The river is significant. The Danube plays quite a large role in this book as it zigzags through the Balkan crazy-quilt of religions, languages and fatherlands:

"The river {Khristo} knew from hours of droning in the dusty schoolhouse, did not stop in Vidin. It rose in Germany, its legendary source a stone basin in the courtyard of a castle of the Fu rstenberg princes in the Black Forest. Called the Donau by all German-speaking peoples, it moved through the Bohemian forests to Vienna, crossed into Czechoslovakia at Bratislava, where they named it the Dunaj, turned south through the Carpathians into northern Hungary, divided the twin cities of Buda and Pesth, flowed south into Yugoslavian Serbia, passed Belgrade ... roared through the Iron Gate -- a narrow gorge in the Transylvanian Alps -- and headed east, serving as a border between Romania and Bulgaria ... Then, at last, it turned north for a time and split into three streams entering the Romanian delta ... where it emptied into the Black Sea, bordered by the Russian Crimea and Turkey, where the Caucasus Mountains ran down to the sea, where Europe ended and Asia began."

Khristo flees home at the invitation of the local Comintern agent, already in place for the export of subversion. He goes to a cold and somber Moscow, a city braced for Stalin's purges. He is recruited by the NKVD and begins a brutal course of study that includes the cold-blooded execution of a German spy in the basement of the Lubianka Prison. The treatment of the ruthless, ascetic Bolshevik mentality approaches the excellence of Arthur Koestler's "Darkness at Noon."

Unbeknown to their Soviet masters, a few of the students at the polyglot intelligence school -- a Pole, a Serb, a Jew, Khristo -- have formed a private cell: Brotherhood Front 825. "It occurred to Khristo, staring up at the Russian sky, that if you had nothing else in the world you could at least have a secret." Throughout "Night Soldiers," the Front will appear at critical moments -- its monogram scrawled on a sunken Danube barge, or listed innocuously in the personals column of a Paris newspaper.

Khristo goes off to fight in the Spanish Civil War, and all the paraphernalia of that most romantic of modern conflicts is paraded: Catalan anarchists, international brigades, the Condor Legion. Warned of his impending arrest by the NKVD, Khristo flees to France and obtains employment as a waiter. From this vantage, he witnesses the revels of the beau monde on the eve of war -- scenes right out of an old copy of Paris Match.

The plot, though fast-moving, is always carefully worked out. There is an OSS interlude, by far the weakest section of the novel -- Furst's Americans are oddly lifeless amid these garlic-smelling Europeans. Back in Paris, the attractively self-reliant Khristo is arrested by French counterintelligence and mysteriously freed when the German Army breaks through the French defenses. After further adventures in the Resistance, he boats down the Danube for the OSS, trying to snatch an escapee from the Gulag who has a list of Soviet intelligence personnel.

Furst is so good that it pains to criticize. This author's fertile imagination sometimes runs away from him and produces a newsreel and not a novel. The footage is marvelous, to be sure, but nevertheless overly cinematic, rather like one of those TV "docudramas" in which every detail is painstakingly authentic. Accuracy of detail cannot make up for weakness in the development of character, as in the inferior depiction of the American agent.

Nevertheless, the idea of portraying the beginnings of the Cold War in the rubble of 1945 Eastern Europe is ingenious. The chase down the Danube is fully satisfying, and there are elegant forays into the craft of espionage -- secret messages and such. Best of all is the chilling trail of treachery and betrayal, as the Russian Revolution -- in the guise of the NKVD -- devours its adherents.

The reviewer is an assistant editor of Book World.