NEW YORK -- Five hours is a mighty long time for a playwright -- even a great one -- to spend clearing his throat. That sentiment was often provoked, unfortunately, in Parts 1 and 2 of "The Coast of Utopia," Tom Stoppard's exhaustive portrait of the turbulent, politically radicalized Russian intelligentsia in the mid-19th century.

So it comes as a pleasant surprise that in the third and last installment of this epic work, which opened this week at the Vivian Beaumont Theater, the lengthy preliminaries finally have given way to a story of historical suppleness and sweep. In depicting the bitter, waning years of influence of the trilogy's pivotal figure, the pamphleteer and reformer Alexander Herzen, Stoppard at last finds a satisfying way to bind the intimate aspects of this vast mosaic to those of grander significance.

The ability to sift the labyrinthine events that eventually lead us to Part 3 might owe as much to forbearance as curiosity. The arc of the trilogy extends from the feudal Russia of the 1830s to the restive 1860s, when the serfs are freed by a new czar and a generation of tougher young revolutionaries is beginning to spread its ideas about a worker-led society.

Sitting through all eight hours of "Coast of Utopia" (which can be spread out over weeks or achieved during Lincoln Center Theater's special one-day marathons), you get the rare theatrical experience of watching a nation's political identity being nourished. As recounted from the perspective of Russia's intellectual elite, the war for the country's soul is waged on a vigorous philosophical battlefield, its soldiers being the assorted progressives, socialists, nihilists, anarchists and other types of believers, all convinced that theirs is the one true Russian political faith.

Stoppard's audacious conceit -- that such a story can even have a life on the stage these days! -- makes you enormously sympathetic. But that does not translate into consistent engagement. I wouldn't presume to suggest which episodes are not crucial. I do know, however, that in the endless theatrical revolving door of poets, lawyers, critics, emigre politicians, activists, Chartists, nationalists and communists, my interest waned more than intermittently. And aside from a few piquant performances -- Billy Crudup's Belinsky in Parts 1 and 2 and Amy Irving's Maria Ogarev in Part 2 -- the actors tended to ebb and flow through the events in so many forgettable waves.

Until Part 3, that is, a 2 1/2 -hour trilogy-capper subtitled "Salvage." (Part 1 is called "Voyage"; Part 2, "Shipwreck.") "Salvage" does not so much tie up loose ends as allow us a deeper contemplation of where the threads of Herzen's life as an activist-in-exile take him.

Obsolescence is, perhaps, an occupational hazard for a political visionary. At some point the prevailing wisdom catches up, or even passes him by. "Salvage" charts Herzen's fall from the pedestal of political martyrdom.

Living comfortably in London off family money, the Herzen of Part 3 is a man in middle age whose zeal has been tempered by personal tragedy. In his trying to reach moderate elements and even government officials, the paper he publishes in London for consumption back home loses its cachet as a radical organ. The new Russian generation, incensed by the continuing stranglehold of the czarist regime, wants to read about something more extreme than mere reform.

We know how all this will explode in blood-soaked revolution 50 years hence; there is, in fact, an air of inevitability hanging over "The Coast of Utopia." In director Jack O'Brien's superb staging, each part of the trilogy begins with the same image: Herzen, played by solid, always-watchable Brian F. O'Byrne, being engulfed by an angry sea.

In Part 3, the idea of events consuming Herzen takes on a poignant cast, as the impact fully registers of the loss of his loved ones and his prestige. As depicted in "Salvage," Herzen's is a voice of reason shouted down in the turmoil of the time. Not for nothing is that more celebrated rabble-rouser Karl Marx given a speech near the end of the trilogy, delivered by Adam Dannheisser in a shaft of white light. It's Marx, not Herzen, who's destined to be the beacon.

Martha Plimpton, playing a woman Herzen conveniently turns to -- even though she's married to a friend of his -- not only makes for a wonderfully impetuous life force, but also a nifty counterpoint to the severe German nanny portrayed by Jennifer Ehle. As Herzen's friend Ogarev, Josh Hamilton provides a finely nuanced account of a man with all too human weaknesses.

For unalloyed strength, however, little could beat O'Brien's fluid textual choreography or the elegance of Bob Crowley and Scott Pask's gleaming sets, which help the characters in Stoppard's sometimes overly busy trilogy to seem as lithe as figure skaters.

The Coast of Utopia, Part 3: Salvage,by Tom Stoppard. Directed by Jack O'Brien. Costumes, Catherine Zuber; lighting, Natasha Katz; original music and sound, Mark Bennett. With Richard Easton, Jason Butler Harner, Ethan Hawke, Kellie Overbey, David Harbour. About 2 hours 40 minutes. Through May 13 at Lincoln Center Theater. Call 212-239-6200 or visit