Toni Collete gives the performance of her career here and quite likely the best female performance of the year

When the matriarch of the Graham family passes away, her daughter Annie (Toni Collette) and her family (Gabriel Byrne, Milly Shapiro and Alex Wolff) begins to unravel cryptic and increasingly terrifying secrets about their ancestry.

'Hereditary' is a difficult film to process once the credits roll, as the film is leaden with such deep subtext around the forms of family, ritual, grief, gender roles, and about a dozen other topics that trying to parse them all and makes sense will inevitably tie you up in knots. More to the point, trying to break it down and rationalise what you've just seen is a way of coping with the film's unbearably terrifying atmosphere. It's a way of giving it distance, and even when the film shifts gears in the third act into truly bizarre territory, you're still trying to keep it all at arm's length because it so truly will terrify you to the core that it's probably for the best.

That might seem like hyperbole, but there's so much in 'Hereditary' that goes beyond just the simple tactic of build up and pay off in scares. There's moments of dramatic tension released that are just as horrifying as seeing something creep behind the protagonist or an apparition appear behind a shelf or desk. For example, one scene involves Toni Collette's tightly-wound artist mother unleash a volley of simmering rage on her son, Alex Wolff, that's just swallowed by him and witnessed blankly by her husband, Gabriel Byrne. It's the kind of horror that isn't violent physically, but violent emotionally and that in itself is more horrific. This, in turn, gives the supernatural elements to the story a cushioning of emotional reality and substance and makes it even more disturbing and frightening.

Toni Collete gives the performance of her career here and quite likely the best female performance of the year, alternating between a woman possessed entirely of grief and then - in the blink of an eye - so cruelly self-centered and emotionally distant that you'd wonder how it's possible that she's even human. Her willingness to be that raw and the ability to convey every single shred of emotion with both minute gestures and broad strokes is incredible. Likewise, Alex Wolff gives a truly nuanced performance and has a tenacity and depth that's far beyond someone of his years and points to a bright future. Gabriel Byrne, meanwhile, truly understands the meaning of being a supporting actor - for both the audience and the actors around him - and Milly Shapiro, though a small presence in the film, is unforgettable.

It's hard to break down exactly what 'Hereditary' is about without giving away huge chunks of it and how it was that writer-director Ari Aster conjured the story into being. For a director working on his first feature-length film, there is such confidence and certainty in every frame of it and without any sense of showboating or pointless grandeur. It's all arranged in a way that has such a layering of purpose and intent that there isn't an ounce of fat on its two-hour running length. Aster draws the tension out like a blade and you're constantly waiting for the slice - but when it comes, it's done with an almost light touch, as if it understands that the tension is more exciting - if that's the right word - than the payoff.

If there's a criticism to be made against 'Hereditary', it's just that - that the endless ratcheting of tension and atmosphere becomes too much, and that the slow-burn approach can easily be read as boring. 'Hereditary' does absolutely test your patience, but it's not done in a way that it luxuriates on any one moment or lulls you into a place of calm so that it can bring you out of it to shock you. Rather, 'Hereditary' just keeps it so that you're just waiting for it at every scene. Using a droning score of wails and staccato strings mixed with a deft use of colour and framing, 'Hereditary' sets you on edge from the opening scene and pulls it right through to the very end.

'Hereditary' is the kind of horror that boldly strikes out into new territory in the way that 'Rosemary's Baby' or 'The Exorcist' did, and offers a fresh perspective on the horror of family and the monsters within the walls of your home.