Sundance: "Joshua."

Brad Cairn (Sam Rockwell) works in finance. Abby Cairn (Vera Farmiga) has just given birth to their second child. They live in a gorgeous renovated prewar apartment near Central Park with all the trappings of the urban near-upper class. Their newborn daughter, Lily, has already been outfitted with a high-end crib, stroller and baby monitors. Their son, the somber Joshua (Jacob Kogan), is a piano prodigy who attends the kind of school in which the boys are outfitted in blazers. He's also, as envisioned by filmmaker George Ratliff, whose last film was the excellent documentary "Hell House," an amalgamation of Damian from "The Omen," Rhoda Penmark from "The Bad Seed" and Cameron Bright's character in "Birth" — an emotionally remote, terrifying mastermind in a boy's buttoned-down shirt.

The horror of "Joshua" is gradual and pervasive — the film starts off on the outskirts of a creaky afterschool special set-up about an older child feeling jealous of the attention being paid to a infant, but develops into something more unsettling. The idea that one's child could prove inherently alien and threatening is not, as the film itself acknowledges (note Farmiga's chic "Rosemary's Baby" crop of hair), a new one to the screen. "Joshua" puts a vicious twist on the concept by aiming at the aspirations of upwardly mobile couples to do everything right and their own way. The Cairns are both aware of and aloof from their own affluence — "Are we these people?" Abby mutters in abhorrence after an inane exchange with various parents of Joshua's classmates. When things start going wrong, they're small-scale disasters out of a liberal parent's nightmares. The baby won't stop crying, but Abby doesn't want to hire a nanny, and eventually the stress plunges her into postpartum depression — she's put on anti-depressants and can no longer breastfeed. The penthouse apartment upstairs is being renovated and noise is unceasing. And strange little Joshua has a habit of questioning, with heartbreaking earnestness, his parent's love for him. Relatively paltry stuff, all of it, but the combined weight is enough to have Abby on the verge of a breakdown and Brad ready to quit his high-flying job in order to shore things up at home, while also beginning to suspect that their problems have one improbable source: their son.

Ratliff manages to coax tension out of mundane domestic settings; he also finds room for a scattering of dark humor — Joshua's most ingenious act of aggression is, following a trip to church with his grandmother, to declare to his areligious parents his eagerness to be born again. Joshua is a magnificent embodiment of an unspoken parental fear that perhaps your children don't care about your good intentions, that perhaps they don't even want the life you're trying ever so carefully to give them. It's a fear that, given the reflexive condescension with which Abby and Brad treat Brad's religious, suburban parents, is not so unreasonable.

"Joshua" paints itself into a corner at the end, but that final sense of deflation fits in with the film's own tendency to cut dread with the everyday. It's still an impressively subversive tweaking of the horror genre, and a memorable one.

Fox Searchlight acquired "Joshua" at the festival and will presumably release the film sometime this year.

+ "Joshua" (Sundance)