Let's get something out of the way first: this is not, as the hype would have you believe, one of the most terrifying films ever made. That's a fact, not a fault - even if you've sat through more horrors than hot dinners. But while The Babadook doesn't serve up jump-out-of-the-seat moments by the dozen, it has plenty of other dark treats.

It's brilliantly acted, beautifully shot, has loads of tension and announces newcomer Jennifer Kent as a writer-director of real class and depth. Her story of a mother and son trying to find their way in the seemingly endless forest of loss will have you thinking plenty in the days, but more especially nights, after you've seen it. This is not so much a case of feeling safer with the light on, but of being thankful that there's someone snoring close to you.

Samuel (Wiseman) is a super-smart but decidedly unsteady six-year-old who lives with his widowed mother Amelia (Davis) in an old house where the creaking floorboards are vastly outnumbered by painful memories. Amelia's husband Oskar died the day Samuel was born - in a car crash while bringing her to hospital. Samuel talks about the day in the matter-of-fact way that kids who don't understand the never-heal nature of bereavement do.

For Amelia, however, the day is a complete no-go, so much so that Samuel's birthday is even celebrated on a different day. Down in the basement all of Oskar's stuff is packed away; up in Amelia's head there's even more pushed into corners and hidden from view. And things are about to get a lot worse - for both mother and son.

When Samuel finds a bedtime story book called The Babadook in the house, Amelia welcomes it as a change from pigs and wolves. But when she starts reading it she's disturbed by the images, the declarations and the fact that Samuel is all set to create a new reality around the character. Amelia already has her work cut out with the boy; in the days ahead she'll face things she never thought imaginable in even her most soul-searching and troubled of nights.

It's been a good year for films -12 Years a Slave, American Hustle, Dallas Buyers Club, Locke, Calvary, The Guest - and Kent's debut will rightfully take its place on many a 2014 best-of list. It won't be the last time she'll feature, and the fact that Kent has said there'll be no Babadook sequel suggests we're in for a right adventure with someone who won't play by the rules. She's right, too: a few more scares aside, she has said all she can possibly say with this story. Chances are she'll never work with better actors.

Directors often talk of the casting process as a kind if alchemy. Well, Kent really did find gold for her two-hander in Davis and Wiseman. Davis brilliantly mixes sublimated rage and longing with parental guilt. Wiseman plays a kid you feel huge amounts of sympathy for but would run a mile from. The director of another great Australian film The Hunter, Daniel Nettheim, said that when working with children there's not a lot of technique to fall back on, and there's only so much you can ask them to do.

Wiseman didn't get the memo because he is Davis' equal in every scene here and is living the part rather than saying his lines - Harvey Stephens in The Omen and Haley Joel Osment in The Sixth Sense have some serious competition. There's one scene here in the back of a car that's so startling in its power that grown-up actors should watch it again and again. 

The Babadook is at times slow moving - far from the fast edits fixation of modern horror - but it can be argued that Kent's pacing just adds to the slow-dripping dread and heartache as two people with very different needs push each other to extremes. You'll want the best for them throughout, while expecting the worst.

Harry Guerin