Sure enough, “Stalin” calls to mind the Don-and we don’t mean the river. Like the young Corleone, Duvall’s Soviet ruler gets his career started with robbery and assassination while surrounding himself with lots of swarthy, mustached thugs, none of whom he trusts. Duvall even sounds like a Georgian De Niro when he launches yet another bloody purge by growling at a flunky: “Geef me da list of dese bastards.” Still, nothing rings false. When you think about it, Stalin really was a kind of capo di tutti capi, except that the scope of his butchery reached just a tad beyond the interfamilial.

But what most fascinates about this TV biography is watching Duvall, arguably America’s most multifaceted actor, crawl inside his role. Like the late Laurence Olivier, Duvall works from the outside in, using makeup, mannerisms and accents to locate the soul of his character. Cunning, sadistic and paranoid, his Stalin resembles Olivier’s Richard III: pure malignity made chillingly human. And never more so than in Stalin’s domestic moments-spitting in his sons face and wagging a scolding finger at a portrait of the wife he drove to suicide. Whether or not this is the real Stalin, it’s a mesmerizing study of a despot turned psychopath who bit off a quarter of the globe.

The tottering Gorbachev regime gave the American filmmakers unprecedented access, and it shows. Here we are inside Lenin’s actual Kremlin apartment. Now we’re at a banquet in the czar’s opulent ballroom, now in a fetid Moscow prison. The film even visits Stalin’s country house in Kuntsevo, where Papa Joe entertains daughter Svetlana with a clumsy impression of Charlie Chaplin, his favorite movie star.

If only the rest of the film worked as nicely. True, it’s all here: Stalin’s reign of terror, which claimed more victims than Hitler’s, his mercilessness toward comrades as well as rivals, his drunken collapse when the war seemed lost. Too much of it, though, seems overstuffed and underilluminated. The incessant narrative voice-over (“Kamenev and Zinoviev were intellectuals . . .”) substitutes telling for showing. Nor does it help that the dialogue occasionally lapses into docu-drama hokum (“You’ve come a long way from the Ukraine, Nikita”). Only Duvall’s genius for infusing voltage into almost every scene keeps this bio-epic emotionally charged. Which is reason enough to watch it.

By unsettling coincidence, the film crews found themselves in Moscow during the Soviet hard-liners’ abortive 1991 coup. While dining in a hotel restaurant, recalls producer Carliner, “I noticed a group of humorless, colorless men at a central table. The next day I would see them on CNN. It was the coup plotters themselves.” All of which should suggest to HBO the perfect sequel: geef us da story of dose bastards.