It’s wintertime in modern Stockholm, cold, gray, relentlessly snowy. Two pre-teen loners, a boy and a girl, meet and bond. That’s “Let the Right One In” — except for one important detail.

The girl, Eli, is a vampire. Like the boy, Oskar, she’s 12. But she’s been 12, in her own dry words, “for a long time.” In the conventions of vampire lore, that could mean centuries.

Swedish director Tomas Alfredson’s film is based on a novel by John Ajvide Lindqvist, who also wrote the screenplay. The title seems to be a reference to vampire visiting etiquette. Oskar and Eli are skillfully portrayed by Kare Hedebrant and Lina Leandersson.

Oskar’s apparently gay dad lives in the country, his mom in an urban apartment, and the boy is shuttled between them. At school, he is routinely bullied. While venting his frustrations on a tree with his hunting knife one night outside his mother’s apartment, he looks up to find Eli curiously looking on.

She explains that she’s a new neighbor. Sensing that she, too, is an outsider, Oskar invites her company even though Eli sometimes smells funny and seems impervious to the cold. She soon agrees to go steady even though neither is sure what it means. Later, after mentally connecting a couple of local murders with Eli’s habit of turning up with blood on her mouth, Oskar perceptively concludes that his new pal is a vampire.

Eli doesn’t deny it. She regrets the killings, but a girl’s gotta live. Oskar accepts Eli’s condition as matter of factly as she confesses it.

Eli encourages Oskar to stand up to his tormentors at school. He does, but with consequences that play out in the movie’s gruesome penultimate sequence.

Considering the body count and the volume of blood spilled (or consumed), the film should be much more gory than it is. Credit Alfredson’s restrained direction, Lindqvist’s tasteful script, which deigns to unduly sensationalize the violence, and the cinematography of Hoyte Van Hoytema. His images are vivid but tame by genre standards, and sometimes are almost painterly in their composition.

Even within its restraints, “Let the Right One In” is not recommended for youngsters. Mid-teens might relate to the loner protagonists, however, and discriminating older viewers should appreciate the film as fine and subtle movie-making. It’s a vampire movie, yes, but also an appealing coming-of-age tale and pre-teen romance.