A cheap film about a bad seed

You really want to love a movie about an evil kid with the nerve to write his own theme song, especially when the song, in its creepy insistence, is a little bit "Ben" and a little bit "We Belong Together." The closing credits for "Joshua" say Dave Matthews wrote the song, but it's crying out for a Mariah Carey remix. Sadly, that winking little number comes well after this tiresome potboiler has worked your last nerve.

The trouble with very-bad-kid thrillers is that your own parental instincts kick in. Mine certainly kicked all over "Joshua ," which gives us a demon seed for our times. Played by Jacob Kogan , acting in his first movie, 9-year-old Joshua is a blank face of menace. Sitting at the front of his prep-school class in that little blue blazer, smart red tie, and khakis, he looks like a pee-wee Republican. But there's nothing natural about him. It's as if Kogan Googled "son from hell" and downloaded the results into his performance. Some viewers will see a deeply disturbed little boy. Others will see a robot. I was disappointed that no one bothered to check for circuitry.

But "Joshua" is the sort of movie in which nobody does what you would do: like spank or demand an extra-strength time out. The movie purports to be about the hassles of high-class parenting. Joshua's daddy, Sam Cairn (Sam Rockwell ), is some kind of Manhattan financial type. His mother, Abby (Vera Farmiga ), just had their second child and doesn't do much more than pout, yell, and tearfully curl up into a ball -- although her haircut (short, wild, chic) says, "I could run an art gallery." They live in an expensive-looking apartment on the Upper East Side, and they do so nanny-less . The movie makes this choice sound moral and brave. But "Joshua" suggests that this is why God invented nannies.

Sam and Abby seem to be so confused about how to care for their new daughter that you wonder how Joshua became such a well-adjusted, gifted pianist in the first place (Bartók at 9!). But that's the secret point of this movie: Yuppie families make prodigies in their sleep. Of course, seeing the way his parents dote on his sister gradually sends Joshua over the edge. While everyone sings "Twinkle, Twinkle Little Star ," he vomits. He demonstrates an interest in mummification. He wants to give his old toys to the poor -- for "a new start." Soon drugged-up mom is losing her mind, important people are pushed to their deaths, and beloved animals turn up dead.

This is a cheap movie that doesn't know it's cheap. If Sam and Abby turn around once and are spooked to see Joshua standing nearby, they do it a dozen times. And having the kid threaten to shove an occupied stroller down the steps of the Brooklyn Museum, à la Sergei Eisenstein , is painful to watch both for film snobs and snobby parents (does he know how much that stroller costs?). There are also dips into religion -- Joshua's evangelical granny (Celia Weston ) wants her Jewish grandson to become born-again -- that feel extraneous to the story while straining to deepen whatever "Joshua" is supposed to be warning us about.

George Ratliff directed, and wrote the script with David Gilbert , and you can tell the movie wants to be a kind of "Rosemary's Baby " or "The Omen ." But it wants that all too desperately. This is an exercise in trash that's afraid to reek of anything. Aside from its contempt for mommies, there's nothing sinister about "Joshua." Or maybe what's sinister about it seems too improbable to be persuasive entertainment. And that improbability, under these circumstances, is banally narcissistic: What if we raise a little genius who grows to hate us? Joshua is a figment of bourgeois parental paranoia: a Montessori nightmare come true.

Wesley Morris can be reached at wmorris@globe.com. For more on movies, go to boston.com/ae/ movies/blog.