Although I love a good twist ending just as much as the next guy – especially in a juicy genre flick like Split, The Charmer, or Arrival, where the twist turns everything you thought you knew about the movie on its ear – nothing ruins my inflight flow quicker than a bad twist ending in a halfway decent movie. And though describing writer-director Ari Aster’s Hereditary as halfway decent is being overly generous, the film does have enough truly terrifying moments early on to at least make the first hour or so watchable.

Unfortunately, after a bizarre death by beheading midway through, things take a turn for the worse and never really recover. And as lame and truly unscary as the climax of Hereditary is, I still hate to ruin the ending for anyone, so, all I will say is that if I knew what this movie was about before it started, I would have run screaming with laughter in the other direction. Seriously. It’s that stupid.

I’m cool with retro-minded thrills and chills, but the payoff in this dreary, weirdly off-putting psycho drama is straight out one of those spooky Perils of Sin church comic books from the 1950s. And worst of all, it’s not even that original. Unless, of course, you’ve never seen Rosemary’s Baby, Suspiria, or Nicolas Roeg’s Don’t Look Now.

However, at the end of the day, it’s Hereditary’s turgid, humorless approach to its completely outlandish storyline that really does it in. I mean, if your gonna go this balls-to-the-wall crazy, at least make it kind of funny.

Starring The Sixth Sense’s (speaking of twist endings!) Oscar-nominated Toni Collette and Gabriel Byrne (Miller’s Crossing, The Usual Suspects) as Annie and Steve Graham, Hereditary opens with the couple dealing with the death of Annie’s emotionally disturbed mother after a long illness. Crippled with grief and guilt over her inability to connect with her mother for most of her life, Annie is also troubled by the effect her mother’s death is having on her and Steve’s teenaged children, Peter (The Naked Brothers Band’s Alex Wolff) and Charlie (played by newcomer Milly Shapiro).

And when Grandma’s anything-but-benevolent ghost begins appearing to first Annie and then Charlie and Peter as well, Annie turns to a new friend from her grief support group for help. But when that friend is played by The Handmaid’s Tale Emmy-winner Ann Dowd, you just know something really awful is abrewing.

Much of the movie fails to live up to the expectations of the first-rate trailer or the promise of the always excellent Toni Collette in anything. But one of Hereditary’s few bright spots is the production design work of budding indie art director Grace Yun (First Reformed, Beach Rats). In the film Annie is an artist who crafts very detailed and deeply unsettling dollhouse-sized miniature scenes that mirror the most traumatic events from her life and Yun’s work on these tiny tableaux is breathtaking. Cold, precise, and scary as hell, even if you forget everything else about this half-baked horror flick, those creepy little dolls in hospital beds and bloody car accidents will haunt your dreams forever. Really scary stuff!

Now playing on select EVA Air, Qatar Airways, Emirates, and United flights worldwide, Hereditary is also available via streaming at Prime Video, iTunes, and Google Play.