When I was six, I was pretty sure that Santa Claus did not exist, but I wasn't certain. There were so many stories, and they were all consistent. Was it just coincidence that each report corroborated the last? I knew that flying reindeer, a fat man in narrow chimneys, and visiting every house on Earth were all implausible, but I didn't have any way to find out for sure whether the winks of grownups meant Santa was a hoax, or whether there was some grain of truth to the myths. Maybe each neighborhood had its own Santa Claus who had keys to all the houses on the block.

First-time director Tomas Alfredson, working from a screenplay by John Ajvide Lindqvist (who also wrote the novel), captures that cusp between believing childhood myths and understanding how the world works. Oskar (Kare Hedebrant) is twelve years old, and he thinks he has discovered vampires.

Oskar's striking blond hair might have made him popular in the U.S., but it doesn't help him in Sweden where he lives. He's scrawny and poor, and the other kids bully him, so he prefers solitude. He works on his Rubik's cube or sits on the playground equipment in the courtyard of his apartment building in the long, cold, dark evening. He is a little too interested in knives, but he doesn't go around killing cats or anything. He's afraid of violence, but he is fascinated by death.

Oskar has noticed a new girl (Lina Leandersson) in his apartment complex. Eli is shy and quiet too, and she might be poor because she doesn't wear shoes in the snow. And she doesn't treat Oskar like a freak, so maybe she could be a friend.

Let the Right One In follows some other characters too, without telling us who is important to the story or why. For instance, there's a normal-seeming old man who murders people in the park. That's partly why the movie is so engrossing; it doesn't tell you anything directly. It shows you characters and their behavior, but it leaves it to you to piece together what it all means. That's not to say that it's vague; rather, it asks you to participate. It gives you two and two and leaves it to you to come up with four.

For example (and without revealing too much), there isn't a specific moment when the entire audience will collectively connect the murderous old man to the story of the kids. But ask anyone who has seen the movie and they will be able to tell you how the old man fits in. We all figure it out at different moments. And when we do, it's a satisfying "aha" moment.

That approach to storytelling--asking the audience to learn by watching and deducing--fits nicely with the Oskar's age. He's figuring out how the world works. He probably knows that Santa Claus isn't real, but he's not sure about vampires yet. If they're not real, why are there rules, like garlic bulbs or having to be invited into a room? Being a twelve-year-old, he doesn't have any way to find out for sure whether they exist, but he's eager to learn the how of vampires, regardless of whether they are real or make-believe.

I won't spoil any of the movie's surprises. Suffice it to say that a satisfying story lies at the heart of Let the Right One In involving Oskar, Eli, vampires, bullies, and the murderous old man.

If good storytelling and a smart, observant character were all Let the Right One In had to offer, it would earn a recommendation. But a half-dozen shots leap off the screen as gorgeous, surprising, or perfectly staged. There is a scene in a swimming pool that is both beautiful and surprising, there is a scene with motion in the shadows you thought were flat, and there is a sudden conflagration that only appears on screen for a blink, which makes it all the more tantalizingly effective.

One quick shot that generated conversation among my friends was of some computer-generated nudity. The shot was too short for me to understand what I was supposed to get from it (maybe I blinked), but I read it as another example of Oskar's curiosity about the world. He's probably never seen what it is that makes girls different from boys. One shouldn't peek, and yet his curiosity is only natural; he's on the cusp of puberty. For me the scene made the character of Oskar seem all the more real. Yet others thought the shot conveyed information from the filmmaker to the audience about the nude character. If I were Oskar's age, I might go back and look at the freeze-frame to try to figure out what it all means.