"I sat through the scariest movie of the year and now I sleep with the lights on."

Settling in to watch Hereditary will fill you with the same type of gently gnawing fear you would feel if you were standing on the edge of deep lake in the middle of the night, knowing you have to dive in.

You know there are horrors in there somewhere, lurking in beneath those dark depths, but you have yet to fully see and confront them.

Hereditary follows Annie Graham (played by Toni Collette, who is absolutely at the top of her game in this role) an artist and mother of two who is grieving the recent death of her own mother, with whom she had a fraught and emotionally abusive relationship with.

Annie’s husband Steve (Gabriel Byrne) and son Peter (Alex Wolff) appear relatively normal, both respectful but unmoved by the recent death, but it is the young daughter Charlie who appears most shaken by the loss.

Charlie (played with haunting perfection by Milly Shapiro) exhibits a wealth of disturbing  and bizarre behaviour in the opening scenes of the film, including predicting her mother’s death and decapitating a dead bird that has killed itself by launching its body into her classroom window. She then places the bloodied head into her coat pocket.

But blood and gore is not what makes Hereditary so brilliant and so utterly terrifying all at the same time. While there are a few jump scares included in the film, in the same vein as iconic horror flicks such as Rosemary’s Baby or The Exorcist, the atmosphere itself is what is most terrifying.

In this case, most of the fear stems from a sickening slow-burn of storytelling that will force a small nugget of terror to settle in your chest as the events of the film unfold.

In fact, the tragedy that hits the already embattled Graham family midway through the film is disturbing enough in isolation to strike fear in your heart, even without taking into account the dark supernatural forces at play here.

It is this second family tragedy that sets in motion the a chain of events that lead to the film’s truly tragic ending.

In order to try and deal with unimaginable grief, Annie lies to her husband, telling him that she is going to the movies when she in fact attends a grief support meeting. It is there that she meets a seemingly kind woman named Joan who is mourning the death of her grandson (played by Ann Dowd).

When Joan shows Annie how to connect to the spiritual realm and talk to the dead (a word of warning, do not try this at home) it allows an ancient evil to enter the Graham's home and we quickly learn that there has been a much bigger and darker plan in place this entire time.

One of the reasons Hereditary is able to draw such a deeply felt emotional response from the audience is that the members of the Graham family are so richly realised on screen. Their characters are so fully formed that as you watch the hardships hit them, it feels as if real suffering is taking place.

More than once, I had to cheat a little and close my eyes during the Hereditary, which I think was just my body's way of jumping into some primal form of self-preservation. And I'm not even talking about a moment during one of the film's most chilling scenes, where the fire alarm in the cinema went off and we all had to evacuate. Which is slightly terrifying when you take into account the role that fire itself plays into some of Hereditary's most fearful sequences.

But in essence, what I found most horrific about the film was the way that the previously safe ideals of family and home quickly became that fearful danger I had felt looming since the beginning of the film. I watched as every room in that house filled with evil, and how seemingly loving family members became the biggest threats.

In those end sequences of the film, Toni Colette's performance is a thing of true, savage beauty, and one that I continued to see every time I closed my eyes as I tried to fall asleep that night.

When you leave Hereditary, you'll probably feel like you're just fine. That the events of the movie have come full circle and you're now able to step out into the sunlight and leave the horror behind.

Yeah, I thought that too, but I was a fool.

Because when I got into bed that night and switched off the lights, I began to see figures from the movie fill the darkened corners of my bedroom. I also began to hear a very distinct sound that had spelled doom for so many of the characters in the film.

I am an adult woman who is not normally afraid of the dark, but after seeing Hereditary, I slept with the lights on longer than I care to admit.

There are some movies that are so brilliantly made and executed that they take up residence in your soul and refuse to leave, and Hereditary is one such film.

So definitely go and see it, if you dare. Just make sure you have a functioning night light.

Hereditary is in cinemas Australia-wide now. It is rated MA15+.

For more stories like this, you can follow writer and Mamamia Entertainment Editor Laura Brodnik on Facebook.