But getting lost in all the well-earned love for Whitaker is his costar, James McAvoy, the primary focus through which Whitaker’s starburst prisms into its brilliance -- here is another actor who will astonish you with a very different kind of performance, one far subtler, one demanding a kind of mirror-image response. Remember how Ginger Rogers used to say that what she did was even harder than what Fred Astaire did, because she had to do it backwards and in high heels? That’s kind of the position McAvoy is in, and he takes the pushing -- both literal and figurative -- that is doled out both to his character and to him as an actor, and he uses that to create a finely drawn, understated portrait of a young man whose impetuousness leads him to the hard boundaries of his own limitations and fears. McAvoy doesn’t just take what is thrown at him by the ferocious Whitaker -- he catches it and makes it his own.

Maybe they should give out an Oscar to acting duos. Whitaker (Everyone’s Hero, American Gun) and McAvoy (The Chronicles of Narnia: The Lion, the Witch and the Wardrobe, Rory O'Shea Was Here), as impressive as they are separately, are even more compelling in opposition to each other, and together they’re on a very short list of actors who’ve done that this movie year.

But what’s the film about? Based on a novel by Giles Foden that’s so pertinent it could well be true, this is the story of a young Scottish doctor, Nick Garrigan (McAvoy), who travels to Uganda in the 1970s, looking for adventure and an opportunity to do some real good, and finds himself swept up in the reign of terror of dictator Idi Amin. Of course, it doesn’t start out looking like a reign of terror -- it starts out looking like a new start for the ravaged nation, and for Nick, too, when Amin, who’s a bit of a nut for all things Scottish, shanghais Nick, who has been working at a remote country hospital, into being his personal physician. And it’s a sweet shanghaining on Nick’s part: it’s all parties and basking in Amin’s charismatic glow for a while, and we’re as charmed as Nick is, at first -- we experience the descent into horror through Nick’s dawning realization that Things Are Going Wrong, and that by the time he knows he has to extricate himself, it’s far too late, and Amin has him cornered, unable to escape.

The hints are there right away, tucked in corners -- this is, ironically enough, such a delicately shaded movie, dramatically speaking, for all that it’s about such an awful, awful man and the power he wielded over even the best-intentioned of people. There’s a threat in the moment when Amin bestows upon Nick a Ugandan passport -- the implication is that Nick will not be seeing his Scottish passport again. There are layers of paradox in Nick’s line, late in the film, in which he attempts to convince himself that he’s been right to let increasingly terrible things go by him uncommented upon : “I’m his doctor. It’s not my job to judge the man.”

The guys behind the camera are as deserving of high praise as those in front: screenwriter Peter Morgan also wrote the equally astonishing The Queen, and director Kevin Macdonald made the riveting “dramatized documentary” Touching the Void Morgan and Macdonald are at the top of their games, too, and they’ve made one of the don’t-you-dare-miss-it films of the year.

(Technorati tags: Last King of Scotland, Idi Amin, Forest Whitaker, James McAvoy)