I'm a big fan of an emerging film genre I call the historical what-if story. "Shakespeare In Love" is the most well-known example of these yarns that skirt around the shadowy edges of known fact to create a fanciful fiction featuring a well-known figure. Others include the current, brilliant "The Cat's Meow," about a murder on William Randolph Hearst's yacht, and "Dick," a great 1999 comedy which presupposed that the Watergate scandal's Deep Throat was actually two ditzy teenage girls who overheard Richard Nixon's conspiracies while working as dog-walkers for the presidential pooch.

"The Emperor's New Clothes" takes a similar approach to the last days of Napoleon Bonaparte. As you may know, history proper records that after his defeat at Waterloo, the distinguished French general and pompous self-declared emperor died in exile under British guard in 1821. But this latest gem of this entertaining genre imagines the diminutive duce escaping back to Paris with grandiose plans to reclaim the throne, only to get waylaid into a more humble life as a middle-class fruit merchant.

Driven by a fantastic dual performance from Ian Holm as both Napoleon and the peasant look-alike who takes his place on the prison island of St. Helena, the film is funny, insightfully human and a delightful lark for history buffs without actually requiring much prerequisite knowledge.

Napoleon's prearranged plan is to slip onboard a supply ship as a galley hand, while a real sailor -- an ignoble, drunken doppelganger named Eugene -- takes his place in the emperor's rather luxurious residence-in-exile. When the ex-emperor reaches Paris, the double is to reveal himself as a fake. "Then," says Napoleon with his chin thrust into the air with prematurely certain triumph, "I shall come forward!"

But what if, after being trained to behave like the brash French dictator, wearing an emperor's expensive robes and being plied with fine wine and food for a couple weeks, the peasant proxy realizes how poshly he can live for the rest of his life by just keeping his trap shut? What if he discovers his own inner tyrant and refuses to admit he's not Napoleon?

And what if the real Napoleon finds his Parisian contact is dead and has to live incognito, helping the man's pretty widow named Pumpkin (Iben Hjejle, "High Fidelity") with her struggling melon cart business because he doesn't trust any of his "more illustrious allies"?

The answer is, both men learn to make the best of it -- albeit one with far more ease than the other. In one ingenious scene the real Napoleon, living as Eugene and frustrated with his newfound insignificance, devises a marketing strategy for Pumpkin's fruit carts as if it were a battle plan. He gathers his "troops," drafts a map of where the best business opportunities lie geographically and plans to "send out children at dawn to scout the terrain!" After rousing Pumpkin's workers with militaristic relish, he declares, "Remember, we conquer or perish!"

Meanwhile, the real Eugene has not only usurped the exiled emperor's personality -- barking at his English guards that "I am not accustomed by being addressed from horseback, especially by those of the lower ranks!" -- but has taken over dictating Napoleon's memoirs and is turning them into the scandalous gossip that is published in Paris after the double keels over from self-indulgence having never admitted his true identity.

In Holm's performances as Napoleon and Eugene, you truly see, believe and even empathize with the humbling transition of one from autocratic egoist to (relatively) modest shopkeep, and in the amusing transition of the other from mousy plebian to power-drunk madman. You understand how the widow becomes attracted to incognito Napoleon as a resourceful provider and a man discovering his gentle, benevolent side. You even feel for sorry for him when just as he's getting comfortable, he's hit by news of his own supposed death on St. Helena and the publication of "his" memoirs. This leads to a resurgence of his former nature that threatens to throw everything asunder with Pumpkin.

Directed by Alan Taylor ("Palookaville") from Kevin Molony's adaptation of the Simon Ley novel "The Death of Napoleon," the film's plot has a few nagging problems. The opening of the story -- structured around Napoleon telling his tale to a little boy who had been looking at pictures describing the emperor's life, defeat and death -- feels uncomfortably contrived until the movie's epilogue ties it all together.

It's hard to fight off some obvious logical questions as well. If Napoleon's supporters could contact him on the island to arrange the switcheroo, why isn't there anyone looking for him in Paris -- and why isn't he looking for them? Why can't his people on the island send word that his replacement has refused to admit his identity so Napoleon at least knows why he's trapped in a life not his own?

"The Emperor's New Clothes" has enough cleverness at its core and such a nimble sense of humor that it overcomes its shortcomings. But it's Holm who brings the story the sense of realism, humanity and personality that gives it life.

It is both comical and telling to see that even when posing as a galley hand, Napoleon has no compunction about cheating at checkers while playing with a friendly crewmember onboard the ship. It is both funny and sad to watch Napoleon's reactions as his trip back to Paris takes him through Waterloo, which has become a 19th Century tourist trap complete with a die-cast soldier toys, nutcrackers in his visage and a "Napoleon Slept Here" sign.

When he finally crosses back onto French soil for the first time, the simple act of relieving himself on the first tree he sees is at once hilarious, portentous and shrewdly metaphorical. All of this comes from Holm's extraordinary personification of his characters.

The movie is worth seeing for many reasons, but 75 percent of them are Ian Holm.