Innocence always calls mutely for protection when we would do so much better to guard ourselves against it: innocence is like a dumb leper who has lost its bell, wandering the world, meaning no harm." So Graham Greene writes in The Quiet American, a novel that plumbs the moral dangers of innocence. That quality is embodied in the character of Pyle, an idealist in early-1950s Indochina who turns out to be a CIA operative working to help a ruthless general gain power. The Boston aristocrat Pyle sees the world in black and white, and the charismatic General Thé, with his Yankee alliances, as a good guy. When Thé's men bomb a milk bar, Pyle walks among the bodies of the dead and wounded in a daze, unable to process what he sees.

In Phillip Noyce's beautiful film version, Pyle is played, in a brilliant casting stroke, by Brendan Fraser, with heavy-rimmed specs and a short haircut that give his big head a squarish look. Fraser demonstrated a comic canniness in last year's unjustly trashed Monkeybone, but here, as the bashful, charmingly awkward Pyle, he demonstrates the kind of acting control he hasn't shown before.

Pyle isn't the central figure, however, in either Greene's story or this screenplay. Michael Caine gives a magnificent performance as Fowler, the middle-aged London Times correspondent whose initial attitude toward Pyle--a combination of bemusement, irritation and protectiveness--turns to horror when he figures out how deep the American's political involvement goes.

The two men are also rivals for the affections of a young Vietnamese woman, Phuong, who lives with Fowler but can't marry him because his wife, back in England, has refused him a divorce. Applying his Back Bay gallantry and social conservatism to this woman from a culture he doesn't begin to understand, Pyle pays court to her, assuming that she'll choose the respectability he offers over a sordid adultery with Fowler. (He's enough of a blueblood to be shocked when he learns Phuong worked as a taxi dancer before Fowler began to keep her; he doesn't realize there's a distinction between that profession and whoring.) Do Thi Hai Yen's graceful, compelling performance maintains the mystery of Phuong's true feelings about her two foreign swains, though she accedes to the wishes of her spinster sister, Miss Hei (wittily played by Pham Thi Mai Hoa), who spots in Pyle the perfect catch.

Fowler is one of those hard-bitten realist-romantics Greene loved to write about, a man whose worldliness and pragmatism don't prevent him from wearing his heart on his sleeve and suffering from pangs of conscience. The Quiet American is his story because he's the one who betrays Pyle to the revolutionaries struggling to undermine General Thé's mounting power. (The movie, like the book, begins with the fishing of Pyle's body out of the Saigon harbor and takes the form of a flashback.)

Caine supplies all the layers of Fowler's motivation, which is simultaneously political and personal, and gives an evocative portrayal of a man who's tried to insulate himself with cynicism and opium but hasn't lost his capacity for pain. In Greene's view, it's that anguished awareness of the world that makes Fowler heroic; he acts with an understanding of the consequences of his actions. Pyle, whose näiveté is both touching and unconscionable, is his opposite number.

Like Fowler, Greene was in equal parts fascinated with and appalled by the damage caused by blundering American innocents. Such figures surface also in The Comedians and in the marvelous screenplay he wrote for Carol Reed's 1949 film The Third Man. (Ironically, the first time a movie was made of The Quiet American, by Joseph Mankiewicz in 1958, the Yankee was played by the war hero-turned-movie-star Audie Murphy and his character and activities were whitewashed. Michael Redgrave played Fow­ler in that version.)

Noyce wisely ends the movie with a montage that brings the story of Vietnam up to America's explicit involvement in the 1960s and '70s, placing Pyle's role in a fuller context. The ending has another purpose, too. Fowler refuses to return home to England, even when his editor no longer wants to keep him in Southeast Asia, because he's fallen in love not only with Phuong but with Saigon. (Christopher Doyle's photography makes it clear why anyone with eyes to see would feel the same way.)

The Quiet American gives us a Saigon whose ripe, rotting splendor is just about to vanish, like the Shanghai destroyed forever by the communists and World War II and the Berlin that Christopher Isherwood discovered in the twilight of the Weimar Republic. Fowler is among the last émigrés to experience the glory of Saigon. The movie is, among other things, a valedictory.