In the highly efficient, relentless little horror movie It Follows, a pretty blonde 19-year-old (Maika Monroe) and her new, older, scummy boyfriend from another town (Jake Weary) have backseat car sex after an aborted movie date. Then he knocks her silly and, “for her own good,” he says, hogties her and announces that she is about to be stalked by a slow-moving phantom no one else can see. It’s a sexually transmitted curse and you either pass it on to someone else or “it” — zombie phantoms shape-shifting in various forms, like an armless woman with breasts bared or a middle-aged guy who sits on the roof of a house — will keep coming back until it slaughters. Violently. “It’s very slow. But it’s not dumb,” says the back seat boyfriend.

It Follows, written and directed by David Robert Mitchell (The Myth of the American Sleepover) is neither slow nor dumb, either. Simultaneously evoking echoes of, quite deliberately, John Carpenter’s Halloween, The Invasion of the Body Snatchers, Scream, and more than a couple of Japanese shockers including Ringu, the movie is set on and around colorless suburban Detroit streets of brick houses and absent adults. The thing, big on Steadicam and a terrific Rich Vreeland score that works the nerves, throbs with an atmosphere of eerie, brooding menace.

It’s all made more powerful and paranoia-inducing because the shuffling stalkers could be anyone, anytime, anywhere. They’re as inexplicable as they are impossible to escape. You know, like the Grim Reaper. And so, naturally, the movie offers no easy payoff at the finale. Mitchell, supercharging his shocks and shudders with subtext about casual sex, AIDS, and STDS, isn’t about to let any of us off the hook — bless his dark, nasty little heart. ***