The reason this movie is so terrifying is because it isn't a horror film: Unlike those demon spawn in The Exorcist or Children of the Corn, Kevin is actually believable. On the surface, as his father points out, he's just a "sweet little boy," but his mother (Tilda Swinton in a magnificent performance, and through whose eyes this story is told) suspects otherwise.

Starring: Tilda Swinton, John C. Reilly and Ezra Miller

Rating: Five stars out of five

Women of child-bearing age should be warned that sitting through We Need to Talk About Kevin will leave them terrified to procreate. Regardless of where viewers stand in the nature/nurture debate, the truth is, raging sociopaths are often born to sweet mothers with the best of intentions, and no amount of unconditional love and jelly sandwiches will prevent them from going on sadistic killing sprees.

It must be said up front, however, that the reason this movie is so terrifying is because it isn't a horror film: Unlike those demon spawn in The Exorcist or Children of the Corn, Kevin is actually believable. On the surface, as his father points out, he's just a "sweet little boy," practising archery in the backyard, reading Robin Hood, messing about on the computer, and attending school regularly.

But when he soils his diaper immediately after it's changed, is this intentional? When a pet gerbil ends up in the garburator, is that a knowing smirk he proffers? Did he coerce his mother into breaking his arm during a particularly bad tantrum, or is she entirely to blame?

Through the eyes of Eva (Tilda Swinton), the situation is -- to fall back on a word that's nowhere near adequate -- complex. And it's through her eyes only that viewers can see, making it all the more challenging as, psychologically, she exists in both the past and present at once. It's a suffocating, fragmented world where, often, the only chronological clue is the length of her hair.

It's also a world soaked in blood, if not literally, then metaphorically. The film opens with a slow-motion shot of an elated, younger Eva rolling around in a pool of coagulated red liquid, which turns out to be crushed tomatoes (she's at the annual Tomatina party in Spain). Later, we see the outside of her house ruined with splashes of red paint, which she attempts to scrape off with razor blades, covering her face with it in the process. In every scene involving a meal, she only ever consumes red wine.

The symbolism isn't heavy-handed, though. Director Lynne Ramsay (Morvern Callar, Ratcatcher), working loosely from Lionel Shriver's book (a fictional account of a school massacre told in epistolary form), manages to be highly artistic in the most subtle of ways: a luminescent curtain billowing into a dark room; a pallid Eva framed against a backdrop of Warhol-esque soup cans; a new house in which nothing has been unpacked, including all the emotional baggage.

Despite not scoring an Oscar nomination, it almost goes without saying that Swinton turns in a magnificent performance, appearing simultaneously vacant and tortured, knowing she's given birth to a nightmare, yet being unable to reconcile that she might still love him. Meanwhile, John C. Reilly as her husband Franklin delivers an effortlessly clueless counterpart.

But the real standouts are a trio of newcomers in the role of Kevin at three different ages: Rock Duer, Jasper Newell and Ezra Miller. Each captures the boy's twisted psyche in a series of pitch-perfect gestures, whether it's methodically snapping crayons in half or grotesquely masticating a chicken carcass. At one point, the older Kevin sits down opposite his mother and begins to extract a series of previously chewed-off fingernail tips from his mouth, lining them up neatly in a row on the table, in total silence. Disturbing is one of many adjectives that come to mind.

In other films dealing with this subject matter, the tendency would probably be to delve into the child's point of view, to explore what prompts a young person to behave this way. There might be scenes with a host of supporting characters --guidance counsellors, fellow students, bullies, family members -- all who share different opinions on the matter. But here, ironically, nobody really talks about Kevin.

Ramsay, instead, is committed to Eva's perspective, and Eva's alone, regardless of all the blanks that remain unfilled on account of this. At a pivotal moment, Kevin's parents are speaking quietly about getting a divorce and he overhears them on the stairs above. His father backpedals, insisting he's heard stuff without knowing the context. Kevin's response is, "Why would I not know the context? I am the context." Indeed, but this is ultimately all he is; Eva remains the focus, and so she should.