Lush costume dramas love to focus on the infidelities of royalty. As you might guess from the title, that's the subject of "A Royal Affair." There are two things that make this film more than just a sexy piece of eye candy, though: First, the affair it portrays really did happen -- it's not simply gossip or speculation. And second, the affair had repercussions far beyond the royal chamber. It helped, in a way, make Denmark what it is today.

"A Royal Affair" is Denmark's entry to the Oscars for Best Foreign Language Film. It is a polished, exciting piece of work.

It opens with Caroline Mathilde (Alicia Vikander) writing a letter to her young son: "I now know I will never see you again. I am writing to tell you the truth, before it's too late."

On screen
'A Royal Affair'
3 out of 4 stars
Stars: Alicia Vikander, Mads Mikkelsen, Mikkel Boe Folsgaard
Director: Nikolaj Arcel
Rated: R for sexual content and some violent images
Running time: 137 minutes

Now we flash back to 1766, when Caroline, a sister of King George III, left England to meet the man to whom she'd been married, in absentia. The 15-year-old is nervous, of course, but above all, she's excited. She'd been dreaming since she was a girl about going to an exotic country to be its queen, with a charming man to attend to -- she'd heard promising things about Denmark's King Christian VII (Mikkel Boe Folsgaard). "I could not imagine a more perfect husband."

Of course, no one is going to tell his intended bride that the man is becoming steadily insane. A pushy stepmother determined to maintain her own position can find it easy, in such a circumstance, to poison an already diseased mind. Caroline gives birth to an heir and then refuses to participate any longer in the charade. She imagines a lonely, quiet life in a strange land. Until she meets another foreigner.

The German Johann Friedrich Struensee (Mads Mikkelsen) is in high demand as a physician to the important, though he'd rather use his skills to help those truly in need. He has written anonymously papers supporting the nascent revolution in France, so he does seem an odd choice for personal physician to the king. But that's just what the secret reformer becomes -- along with the secret lover of the king's wife.

Their affair is not simply one of the body. Struensee opens Caroline's mind -- and, shockingly enough, the king's, too. But there are too many aristocrats struggling for power at court to let either of these things remain secret for long -- and an insane man is vulnerable to all sorts of manipulation. But it's not just the lives of the queen and the doctor on the line. The future of Denmark, too, is in the hands of a very troubled man.

Mads Mikkelsen will be familiar to American audiences from his turn as a Bond villain in the recent "Casino Royale." His talent for being completely charming even while being sternly serious is put to good use here.

But the break-out star is Alicia Vikander. The Swedish actress also enters theaters this weekend playing Kitty in "Anna Karenina." Both roles require a certain naive innocence, followed by a quick jump to resourceful maturity. The beautiful actress can transform herself and our feelings about her changed characters. She's one to watch on both sides of the Atlantic.