The kids just don’t get it, do they? Occidental youth continue to gallivant through the exotic, rudely governed ends of the earth despite Hollywood’s repeated warnings that behind every Buddhist stupa or casbah gate awaits some nightmarish twist of fate. The routine has gotten pretty old by now. One moment you’re taking in a rich eyeful of non-Western scenery, and the next, poor Claire Danes and Kate Beckinsale are behind bars in a Thai prison (“Brokedown Palace”), or Deborah Winger has morphed into a Touareg sex slave (“The Sheltering Sky”), or the sumptuous French actress Virginie Ledoyen, thanks to some diabolical alignment of the stars, is making out in a watery paradise with Leonardo DiCaprio (“The Beach”).

A film that really wanted to up the ante could take one of these freshfaced Westerners abroad and, say, shackle him to a murderous African dictator. How about one with a reputation for cannibalism? “The Last King of Scotland” pairs a young Scotsman with the Ugandan strongman Idi Amin and delivers two hours of taut drama and brisk, gut-wrenching action — and, yes, a forceful lesson on third-world adventures.

The essential premise of this blend of fact and fiction, which is based on a novel by Giles Foden and set in the 1970s, is a bit of a stretch: A young doctor (James McAvoy) volunteering at a village clinic in Uganda happens to be the only medical expert around when Amin’s (Forest Whitaker) convoy gets in a smash-up on a back road. General Amin, who served with Scots during Uganda’s days as a British colony, is partial to Dr. Nicholas Garrigan’s native land (the film’s title refers to one of many titles His Excellency President for Life bestowed upon himself during his eight-year rule). Amin also takes a shine to Nicholas, a brash, candid type, and makes him his personal physician.

Because the filmmakers have done their homework, and because the film ends up as more of a parable about post-colonial Africa than the final word on Amin’s reign of terror, the plot can afford a weak hinge. Nevertheless, it’s a credit to director Kevin McDonald and his fine leading men that exactly how Nicholas got where he is for most of the movie is quickly forgotten.

Mr. McAvoy’s Nicholas is sporting, friendly, obtuse, and totally recognizable; Mr. Whitaker’s rich but loose impersonation (the real Amin spoke an eighth-grader’s English and managed to sit still from time to time) begins with his impressive physicality and could well end with an Oscar. With his terrifying, on-a-dime switches from bonhomie to barbarism, you can feel Mr. Whitaker siphon the schizophrenia of the Olympians into a single modern autocrat — without, amazingly, ever giving the impression he’s trying to steal the show.

Mr. McDonald, best known for his Oscar-winning documentary “One Day in September,” uses the tools of non-fiction filmmaking — mainly zooms and sharp edits — to send the viewer hurtling through one man’s experience of a revolution gone awry.

As a wary co-worker at the village clinic, played by Gillian Anderson, informs him, Nicholas has chosen a “busy time” to arrive in Uganda. Amin has just ousted his predecessor in a coup d‘etat. Nicholas watches him take the stage at an electrifying victory rally where the general’s fearsome, animal charisma charges the air. When Amin announces that Uganda has shaken off the white man’s yoke (despite the fact that the British quietly supported the coup and their agents still prowl the capital), it appeals to Nicholas’s rebellious side, and he is quite happy to take a posh bungalow in the capital in exchange for medical advice and an occasional opinion in matters of “good taste.”

Meanwhile, His Excellency is making regular trips to Libya and having his men hunt down loyalists of the former prime minister, Milton Obote. One day a prison explodes, filling the Kampala skyline with plumes of dark smoke — an allusion to an actual 1971 incident in which several dozen Obote supporters were shoved into a jail cell and dynamited. But before Nicholas can ask what’s going on, he is summoned to bring the son of Amin’s prettiest wife, Kay (Kerry Washington) out of an epileptic fit. The house call sparks a flirtation — an imprudent one, to say the least — whose awful consequences are not difficult to predict.

By maintaining this sort of rat-a-tat-tat rhythm and condensing four and a half years into what seems like a month of plot time, the film makes Nicholas‘s obliviousness more credible: The situation always seems too hot for him to get a handle on what’s really going on. But he is also decidedly callow. He refuses to admit he’s sided with a madman, and tries to defend Amin when a British spy informs him the general’s troops are massacring dissenters and feeding them to crocodiles.

Nicholas gets a cabinet member killed when he thoughtlessly reports him for suspicious behavior. “You did it,” Amin tells him. At this point Nicholas decides he’d like to leave Uganda. But Amin, who might be speaking for all of post-colonial Africa at this point, refuses to let the white man off the hook: “You have stepped deep into the heart of my country,” he says — just not the way your safari tour guide would.

It would be nice if Hollywood took innocence to task this way more often. When her mea culpa moment arrives in “The Devil Wears Prada,” the tyrant’s sidekick simply tosses away her phone and gets out of the limo. Kirsten Dunst’s Marie Antoinette represents, in the Sofia Coppola film that comes out next week, an inheritor of a world of royal privilege that was destined to combust before she was ever born into it — in other words, not her fault.

The girls are getting off easy. Nicholas is just going along for the ride, too, but his ride — as many of the West’s doubts about Idi Amin did — ends, bloodily, at Entebbe, where Amin invited pro-Palestinian hijackers to land with their hostages in 1976. In the early 1970s, many in the West regarded Uganda’s uneducated leader as a mere buffoon. Maybe they didn’t know any better. But the joke is still on them.