What is it about the need for sibling rivalry in some families? Is it simply that one child cannot personally justify the existence of their brothers and sisters? Or, is it something altogether innate, a knee-jerk response to a situation that is out of their control resulting in a give-and-take battle of familial favoritism?

Sam Rockwell, Jacob Kogan and Vera Farmiga are not the perfect family in Fox Searchlight's Joshua

The answer is not necessarily found in Joshua, a disturbing, under-the-skin creepy socio-horror film focusing on an NYC Yuppie couple’s young son (newcomer Jakob Kogan, a real find). The parents, Brad and Abby Cairn (Sam Rockwell and Vera Farmiga), are resettling their nest with a feminine bundle newborn joy failing to notice how their eldest is apparently none too pleased with his sudden shift to ‘second’ favorite.

Joshua is a smart-beyond his years but he is taking a dark turn. He’s also keenly aware of how his mother’s post-partum depression is crippling her sensibilities to the point of mania, manipulating her by picking away at her weak spots (i.e. the baby’s constant crying).

While hedge-fund organizer Brad is busy at the office he is not as neglectful of his family as it first appears. He clearly loves them all, has a strong (if slightly estranged) relationship with his devoutly Christian mother Hazel (Celia Weston) and enjoys his high-pressured job even if his jerk of a boss Chester (Michael McKean) can barely tolerate his subordinate’s paterfamilias peccadilloes.

Things begin to get difficult after Abby is placed into an institution when an accident causes her to become dependent on painkillers. As scary game of hide-and-seek game with Joshua certainly doesn’t help things, either. Suddenly Brad can see the forest for the trees, putting a plan into action to keep his baby girl safe from harm from her brother using any means necessary.

Freshman feature film director George Ratliff (he helmed the Christian amusement park documentary Hell House) drives the suspense, his borderline black comedy script (co-written with David Gilbert, another rookie) keeping the reality-based terror bubbling strongly. The eerie, piano jangling score by Nico Muhly and Benoit Debie’s foreboding camerawork both provide Goosebumps of dread keeping the audience unsettled.

Rockwell, one of my personal faves (and perhaps the most underrated actor of his – and my – generation), is excellent. The bantam thespian walks with a dancer’s grace, his retro hair suggesting a hepcat that is happy with his place in the world and feels he has the edge to handle most things. Not the same for Farmiga’s Abby. She has the difficult task of playing a somewhat unsympathetic character as a mom incapable of caring for her children to the point of insanity, but she acts up a storm here in a highly unorthodox turn. Both actors (in career best performances) make you feel for their desperation, their last-ditch efforts to keep their sanity highly impressive.

There are distinct echoes of supernatural based ‘bad seed’ films like The Omen (dapper, sober-faced lad with a lethal feel charm) and Rosemary’s Baby (spooky Upper West Side digs and the female protagonist’s elfin haircut) but the line stops there. Joshua doesn’t fall for any easy outs (Joshua isn’t the Devil’s child) playing more like a really decent Twilight Zone episode. That said, the film’s final moment feels a bit like a copout and isn’t entirely believable keeping this otherwise unnerving and nasty slice of the American Dream from becoming a true cinematic American Nightmare.

Film Rating: êêê  (out of 4)