Two of the iron rules of moviemaking -- that you can't make movies out of politics, and that serious intellectual themes gum up entertainment -- evaporate before your eyes in "The Little Drummer Girl," a movie of ambitious scope that ingeniously tickles the mind. Like an enchanted escape artist, director George Roy Hill has pulled off that rarest of Hollywood feats -- the thriller of ideas.

Based on the diamond-cut spy novel by John Le Carre', "Little Drummer Girl" tells the story of Charlie (Diane Keaton), a leftist stage actress who is recruited by an Israeli intelligence operative, Kurtz (Klaus Kinski), as a double agent in the war against Palestinian terrorism. Charlie, understandably, balks at first -- like all good radicals, she's been a Palestinian sympathizer -- but Kurtz slyly draws her in by playing to her idealism and, in equal part, her vanity as an actress. "It's the most demanding role you've ever had," he tells her, a chance to perform in the "theater of the real." The clincher is Col. Becker (Yorgo Voyagis), an Israeli war hero whose swarthy good looks leave her revolutionary politics blowin' in the wind.

Unlike most thrillers, Le Carre''s novel doesn't obviously lend itself to the movies. Nothing much happens in it until the end; 500 pages prepare you for the denouement, searching out the nuances of motivation as the net is slowly drawn in. "Little Drummer Girl" is a model of how to adapt a complex novel to the screen. The script, by longtime TV writer Loring Mandel, is a paragon of compression; he leaves some scenes whole, shaves others to an exchange of glances. In a couple of places, he even improves on the careful choreography of Le Carre''s narrative (he has Charlie, for example, mistake Becker for the terrorist Michel, a doubleness misapprised only by the terrorists in the book). And while he lifts much of the dialogue wholesale, he also sharpens it at key moments. Part of what made the book so fascinating was its meticulous attention to detail, and the movie retains the insider's glimpse of the elaborate mechanics of spying, the carefully scripted methods of interrogation.

What makes "Little Drummer Girl" such a special thriller is that the suspense takes place within our own hearts -- the question is not how the characters will end up, but where our sympathies will finally lie. In an exquisite balancing act, Hill draws us first to the Israelis, then to the Palestinians, then back again. When Kurtz first recruits her, Charlie's pro-Palestinian partisanship seems like so much Marxy babble; but in training her for her mission, the Israelis have to inculcate her with the beliefs of her opponents -- they have to convince her the Palestinians are right, and they convince us, too. At which point the wheel turns again.

Issues are whittled to methods of manipulation, spurs to move Charlie this way or that. The movie's portraits of the antagonists come in the play of mirrors: the Israelis seduce Charlie by offering her the close family she never had, and so, too, do the Palestinians. Kurtz frames their situation as that of an oppressed people with no place else to go; the terrorist Khalil (played with magnetic gentleness by the French actor Sami Frey) analogizes his people's plight to that of the Jews. And the symmetries can be much more subtle -- Khalil, for example, has the same tic of whipping off his glasses to make a point as Kurtz. Even love, for both sides, is just a way to get someone to do your bidding.

With "Little Drummer Girl," George Roy Hill establishes himself as Hollywood's master ventriloquist, capable of everything from a jokey homage to the western to black satire to a thriller. Hill is no virtuoso -- his montage of violence in "Little Drummer Girl" quotes limply from "The Godfather" -- but he has paced his movie with a stopwatch. More importantly, he knows how to work with stars. Hill virtually created Robert Redford with his long take of the Sundance Kid at the card table at the beginning of "Butch Cassidy," and here he gives his leads the elbow room they need to create rhythm and mood.

The strategy is rewarded -- Diane Keaton gives the performance of her career. Keaton's face is rife with lines -- she's way too old for this part. Worse, she's brunet, as American as the all-night diner, and attractive only in a gawky, sisterish way. She's all wrong, in other words, as the 20-year-old, red-headed British inge'nue Le Carre' created in his book. But "Little Drummer Girl" makes a virtue of necessity; instead of having Keaton learn a British accent, they've made Charlie an American -- the movie becomes a classic American narrative of an innocent abroad, as if Henry James had written a spy movie. And Keaton's battle against her own physical characteristics only makes her performance more heroic. Looking up through her lashes with her dimpled curlicue smile, she grabs you by the collar and insists she's an inge'nue; and when she goes on to play a terrorist, there's an audible shift in her approach -- she's an actress playing an actress playing a role. She's able to dredge up her daffy Annie Hall persona and use it -- it becomes part of Charlie's shtick. In "Little Drummer Girl," Keaton dares to look silly, and she sometimes does -- particularly in the scenes of her training with the terrorists (it looks like someone transferred her from the Camp Fire Girls). But since "Shoot the Moon," there's a new seriousness in her, a sturdy mantel on which she places the baubles of her old mannerisms.

Klaus Kinski has flat frog's lips and an eagle's gaze; in the recent "Android," he could look dangerously crazy just sniffing an orchid. But here, Kinski tones down his lunacy, adding a suavely murderous avuncularity. His performance is a kind of sly satire of Jewish familial guilt -- warmth comes at the price of toeing the parental line. And Michael Cristofer, as the Palestinian leader Tayeh, does an ingenious Dr. Strangelove turn -- clomping around with a cane and an eye patch, lips parted in a permanent sneer, he limns a cameo portrait of a poignant psychopath. The unfortunate dud of the cast is Voyagis, as Col. Becker; when Charlie upsets her life and her beliefs for this bland teddy bear, it just seems perverse.

If "Little Drummer Girl" throws in with one side or the other, it is with the Israelis, but only because they're more imaginative and efficient players in the game. In this way, the movie's view is the view of spies themselves -- "Little Drummer Girl" is the most trenchant, chilling vision of the psychological fallout of spying since Francis Ford Coppola's "The Conversation." Shot in sallow yellows and hypoxiac blues, it's a coldly Olympian movie -- the struggling partisans seem as pointlessly vicious as rats competing for a discarded cabbage.