It Follows (2014, rated R) is not a movie about logic.

It is a teen sex-horror flick, where sexual intercourse immediately leads to spectacularly bad consequences — in this case a murderous supernatural stalker who can look like “anyone,” but only twice in the movie (that I could tell) chose to look like someone the characters know.

So, we “get” to see young people engage in normal sexual activity: that is, heterosexual coitus; nothing very kinky, somewhat discreetly shot. But the music is ominous, and there is not much erotic about the film, except perhaps for the first sex scene. The fear and horror kill the mood. It Follows might serve as a sort of anti-porn.

The premise is brilliant, in a sick and twisted way. The “It” that follows can take the shape of any human, but in its behavior it is obviously not human. It walks, and walks only, and when close lurches, thereby echoing zombie films, particularly of the classic variety. I won’t elaborate on it at length, especially since, as the movie ran, I kept thinking of ways to work around the premise’s “curse”: why not go island hopping?

What It follows is teen sexual activity, of course, so the easiest metaphor that comes to mind upon grasping the premise is that it sort of works as a metaphor for sexually transmitted disease. Or that ultimate killer of mood, a baby — sexual reproduction.

But one probably shouldn’t expend too much thought on it.

The films is better than most in this genre. Most people find it both brooding and creepy and ominous, on the one hand, and capable of delivering a few shocks of fright, on the other.

Interestingly, these “Its” are in most instances adult, and when adult are usually naked or at least in a state of advanced undress.

Yes, for much of the film, the heroine, a lovely older teen girl, is chased around by naked adults.

This helps conjure up rape fears, as well.

Interestingly, adult characters rarely intrude into the story as anything other than these maleficient “It’s,” and we witness teen life that has very little to do with adults. This is the horror of broken homes.

One of the girl characters is reading an ebook edition of Dostoevsky’s The Idiot, on a curiously designed shell-shaped e-reader. I will leave the passage she quotes from the book, narrated in the film, for other viewers to decide its importance.

Portions of the movie show some evidence of amateurism. Thankfully, not the acting. Mainly, the pulling of focus in some scenes. The score is digital synth, as if in homage to John Carpenter, though videos of classic grade Z horror flicks play in the cinematic background in many scenes.

There is not much humor in the film.

The lead actress is lovely, but not, interestingly enough, in conformity to the usual Hollywood twig-thin fashion model body type.

The film gets astoundingly high ratings on Rotten Tomatoes.