Why? : THE UNQUIET GHOST: Russians Remember Stalin, <i> By Adam Hochschild (Viking: $22.95; 304 pp.)</i>

“Why are you doing this?”

Adam Hochschild heard this question often in the course of his 1991 search for surviving victims and executioners of the mass terror orchestrated in the USSR in the 1930s by Stalin. Why, Russians wanted to know, would an American journalist armed only with a knowledge of their language and a tape recorder assign himself this story? Why now, 60 years after Stalin set up the killing machine that would destroy 20 million of his countrymen, now when only a handful of witnesses survive, and when new threats loom?

Western readers may echo these questions. Why should we be led once again through the cemeteries of the Russian Revolution? Hasn’t Robert Conquest shown us the Great Purges? Alexander Solzhenitsyn the Gulag Archipelago? Nadezhda Mandelstam the plight of the intellectual under Lenin and Stalin? Evguenia Ginzburg the day to day strategies of survival in camp? What is left in the ‘90s for an American writer, an outsider, to see and to report?

The answer is to be found in the absorbing pages of “The Unquiet Ghost” in the narrow window of time available to the Stalinist reign of terror. From previous visits he knew that for at least three decades after the death of Stalin in 1953, silence had prevailed throughout the USSR. Few survivors spoke to foreigners. Secret police files were sealed. Only with the first intimations of glasnost in the mid-80s did signs appear of a yearning to break the silence, to unburden the collective past, to stake the ghosts.

By 1991 glasnost, which means “giving voice,” was in full cry. The problem was that now that testimony was being sought there were few alive to offer it. Hochschild set about to find them.

His journey would take him from Moscow to Siberia, back to Moscow--where for the first time the interrogation transcripts files of several American-born victims of the Great Purge would be opened--back again to Siberia, and finally to the most dreaded corner of the gulag, on the Arctic circle in northeastern Siberia: Kolyma.

In this search he would sometimes be aided by members of Memorial (pronounced Memori-AL), a loose-knit, widespread organization founded in 1987 and devoted to the opening up of official archives of the secret police and to the recording and cross-referencing of data about its millions of victims. Of the several hundred interviews taped along the way, Hochschild chooses a few, the most telling, each showing a different aspect of the dissolution of the Revolution into terror and death, the liquidation of whole generations of citizens most useful to the state. We meet victims and executioners--and those who can only be said to be both.

A powerful metaphor for the impossibility of burying the Stalinist past was the gruesome discovery at a town on the river Ob in 1979, when spring flooding and erosion exposed a mass grave in the bank under the former NKVD headquarters. “These corpses lay at the bottom of the grave, whose floor was the great sheet of permafrost that underlies most of Siberia. In addition, the soil dumped on top of them was dry, sandy, and laced with lime as a disinfectant. The bodies had not decomposed; half-frozen, they had been mummified.” The authorities made desperate efforts to conceal the horror, and Hochschild records the recollections of the townspeople, including those of the daughter of the NKVD regional chief responsible for the thousand murders more than 40 years before.

Elsewhere we meet Vladimir Glebov, a teacher of philosophy, former prison and camp inmate, reader of Emily Dickinson, the “most alive” person the author encountered. Glebov owed his life to changing his name: his father was Lev Kamenev, a principal Bolshevik leader and early victim of the Great Purges.

Perhaps the most wrenching scene in “The Unquiet Ghost” takes place in a KGB office in Moscow. Anxious to demonstrate the “new look” of their agency, KGB officers have opened certain files for Hochschild and a friend. One of those files is that of Arthur Talent, whose misfortune was to be born in the United States. At the time of his interrogation in 1938 he was 21. From the questions and his responses one can feel his mounting fear, follow his hopeless strategies to avoid implicating others in nonexistent conspiracies, and see him finally dissolve in terror, confessing to preposterous crimes, until the interrogation is interrupted, and, as the records show, he is taken to be shot.

The author of “The Unquiet Ghost” combines the strengths of a practiced investigative reporter with those of a philosopher-historian with a sensitive moral compass and the spirit of an enlightened 18th-Century gentleman. He shares with the reader his fascination with the deepest (and most often debated) historical and ethical questions: Were the Great Purges of the ‘30s and their aftermath the handiwork of Stalin alone, or was the entire Soviet Union in collusion with him? Was the deliberate murder of millions of victims known to be innocent the ultimate assertion of his power? Or the executions of the executioners, the Revolution devouring its own? Or was it the systematic perversion of the notions of innocence and guilt, good and evil, and finally the assertion of control over logic itself?

Of special interest to Hochschild is the question of how the Stalinist genocide compares with others, notably the Holocaust and the Spanish Inquisition. In terms of numbers of victims, many of whom were Communists like himself, Stalin may well have been the most murderous tyrant in world history.

Hochschild writes extensively of the phenomenon of denial during and after the long period of terror. He pays tribute to the “small band of clear-seers,” notably Nadezhda Mandelstam. He himself is a prescient moralist: “We want so hard to believe that heroic resistance to evil is always possible, that there still can be angels in a world run by sharks. After all, what about Gandhi, Martin Luther King Jr., Nelson Mandela? Of course you can always resist evil. But to resist and have a chance of surviving is a different matter.”

“The Unquiet Ghost” makes an important contribution to our post- glasnost awareness of the former Soviet Union’s harrowing past--and of its unsettled present. Belonging to a literary genre, which has flourished for centuries, that of “The Voyage of Russia” by a Western observer, it is an illuminating excursion led by a highly qualified guide. As Nadezhda Mandelstam once wrote: “We have to get over our loss of memory. This is the first task . . . otherwise there will be no way ahead.”