“Joshua” is one of those hard-to-classify movies. It’s either a laughable psychological thriller, a mediocre family drama, or possibly, if the filmmakers were being far-sighted, a future third-tier camp classic. Lauded at Sundance and picked up by Fox Searchlight, this half-baked collection of parental anxieties shows that one thing worse than contemporary cinema’s unredeemably sadistic frights is what’s passed off as subtle and smart.

The latest version of the “The Good Son” premise plops the titular creepy kid (Jacob Kogan) in Manhattan, as the precocious son of yuppie parents. Though the family lives somewhere on Central Park West (notorious incubator for “Rosemary’s Baby”), the source of conflict is not Satanism but competition for parental affection in the form of a newborn sister, Lily, who appears pink and fragile in credit-sequence closeups. Throw in mom’s case of postpartum blues and dad’s Wall Street pressures, and you’ve got a family ready to be royally unnerved.

The boy wastes no time. “You don’t have to love me. It’s not like a rule or something,” he helpfully suggests to his father, apropos of roughly nothing. Joshua’s zingers, intoned with level gaze and Teddy Ruxpin enunciation, come early and often, to the point of resembling the morbid smart-aleck type of a sitcom. When not discomfiting, Joshua wakes the baby and disappears before anyone can pin the rap on him. Sometimes, he also spookily tools around in his blazer well after school lets out.

Grimmer deeds emerge — embalming a stuffed animal to name one, followed by the family dog’s suspicious death, then worse — but “Joshua” stacks the deck with a family that never convinces in the first place. Depression dispatches mom (Vera Farmiga) to cuckooland, crudely shoving her offstage simply to drive home her child’s sinister influence. Dad (Sam Rockwell) holds out longer, but he’s obscured by Mr. Rockwell’s congenital beboppin’ shallowness and a script that gooses suspense by sending him sprinting across town.

More important, the parents appear disconnected from the child from the outset, even before we see him going Schönberg on “Twinkle, Twinkle, Little Star” at a school recital. The fear of alienation from one’s own child is, of course, the bread and butter of the creepy-kid genre — a little-remarked sensation among parenthood’s welter of emotions and assault on identity. But George Ratliff, who directs and co-wrote the screenplay, has a tin ear when it comes to building and pacing this story and sussing out a suitable tone.

Not that Mr. Ratliff doesn’t do some spectacular flailing. Besides the rot of the privileged nuclear family, there’s pressure from grandma (Celia Weston), a fundamentalist Christian who’s eager to get her oh-so-scary religious mitts on the unbaptized rascal. Hectoring the parents about Jesus and sneaking the boy to a revival meeting, she yields a religious caricature to hang alongside the casual misogyny of mom’s hysteria. (Perhaps the proselytizing stars of Mr. Ratliff’s claim to fame, a documentary exposé of Christian frightfests called “Hell House,” are too fresh in his mind.)

Another dicey character is Joshua’s swishy Uncle Ned (Dallas Roberts), a Broadway tunesmith who’s always hanging about the apartment with a martini and a mollifying word for his sister. Joshua’s bizarre final exchange with Ned, after the boy has wrought his havoc on the family, must be seen to be believed. I’ve heard it interpreted as merely the capper to the homophobic ring in the artistic boy’s outsider status (ineffably “different” from the other kids), and that gloss is hard to shake.

Even in terms of basic thriller mechanics, “Joshua” relies on a tiresome repertoire of nighttime frights, crosstown coincidences, and double-underlining piano plinks. Mr. Ratliff wrings dry his one good cinematic trick of disorientation, a drifty sense of sound-image synch. Joshua’s Ted Koppel hair helmet is its own uncanny special effect, a sculpted creation so inexplicable that the screenplay includes a crude observational comment from dad (“What is it, made out of plastic?”).

“Joshua” comes with prepackaged roles for an aspiring cast: something for Ms. Farmiga (“The Departed”) to tear into earnestly, something “serious” for Mr. Rockwell, and the child-actor hype of Mr. Kogan as the next big little thing. But despite their mixed efforts, and everyone’s morbid desire for the timeless “Bad Seed” template to swing, the film is an awkward disappointment that simply doesn’t click.