If you don’t know what “sundowners syndrome” is, and have no experience of its horrors, you may not be able to feel the full impact of The Visit. When you first hear about the syndrome, probably when dealing with your aging relatives, it seems as if it must be fictional — a form of dementia that is activated only after sunset.

Night sets in, and elderly sufferers are overcome with symptoms such as angry agitation, paranoia, and hallucinations. They pace, yell, cry, make irrational demands, describe fearful sights only they can see.

In other words, they enact their own pitiable horror show night after night, and writer-director M. Night Shyamalan has made this mysterious syndrome the basis of his amazingly scary new horror film. In it, two children visit their grandparents at their isolated rural home for the first time after a long family estrangement, and are terrorized by the old people’s increasingly bizarre and threatening behavior.

This is a brilliant contemporary move to make in horror, at a time when people are living longer and longer lives, and experiencing more protracted end-of-life suffering. How to care for the long-lived elderly is a pressing problem in cultures that have long since abandoned the multi-generational home, and no longer approve of “warehousing” senior citizens in nursing homes, which are unaffordable anyway for most of the working class. The cultural phenomenon of more and more adults acting as caregivers for their aging parents has generated reams of think pieces in recent years.

In other words, you’re more likely to have to care for an elderly person who lives to be eighty, ninety, or even a hundred, just as you’re more likely to be such a person yourself, than at any time in history.

With this promising material, Shyamalan is apparently working on a comeback, returning to his roots in the Gothic horror film genre where he began with his colossal breakout hit The Sixth Sense back in 1999. It’s been sixteen rocky years since then, as the favorable critical and popular response to Shyamalan’s films collapsed. Even diehard Shyamalan fans who strongly defended the merits of Unbreakable, Signs, and The Village, in spite of those films’ increasingly glaring flaws, tended to lapse into an appalled silence with Lady in the Water, The Happening, and The Last Airbender.

Shyamalan’s slow-motion train-wreck of a career, aggravated by his well-documented egomania, has become something of a morbid cinephile spectator sport.

But in a sudden, unlikely turnaround, this return to Gothic horror seems to have revived Shyamalan’s best instincts. It’s a beautifully shot low-budget film, made for a mere $5 million, the majority of it stripped down to a few characters in one evocative setting, an old farmhouse in Virginia. The remarkable ability Shyamalan demonstrated in The Sixth Sense to compose shots of buildings, outdoor spaces, and empty rooms that somehow conveyed intense eerieness is back in The Visit. The man can shoot horror!

Of course, some of Shyamalan’s worst instincts are present too. For instance, he awkwardly “plants” problematic character traits or traumatic incidents in characters’ pasts that are announced early on and then have to be just as ostentatiously addressed and resolved later in the plot. And he seems unable to leave the “twist ending” out of his narratives, though he handles the one in The Visit pretty well.

Plus he relies on some unfortunately clichéd character types and lame humor — for example, the boy, named Tyler (Ed Oxenbould) is a silly would-be rapper wearing his baseball hat sideways and throwing gang signs like some Vanilla Ice parody in a 1990s movie. This kind of thing requires a lot of patience during the short set-up of the film.

And the denouement is truly terrible — I recommend skipping it entirely. It contains a ludicrous “moral of the story,” plus a return of the children to their former obnoxious selves, before they were seared in the furnace of the old people’s desire to have a “perfect family visit.” Pro tip: just get up and walk out of the theater right after the climactic shot of the grandparents’ house seen through a rainy windshield. I’ll say no more.

But the majority of the film, when the very young are being terrorized by the very old, is highly effective.

Most of the terror is centered on the grandmother, portrayed in an exceptionally frightening way by Deanna Dunagan, a Tony Award-winning stage actor who’s also done a fair share of TV. She has a creepy resemblance to Lillian Gish, an actor most famous for her silent cinema performances in D.W. Griffith films like Broken Blossoms and Birth of a Nation. The grandmother’s otherworldly sweetness of face becomes ever more disturbing as we see it distorted by expressions of zombie-like vacancy, sly scheming, and snarling rage.

If her expressions and behaviors seems over the top to you, you haven’t spent much time in nursing homes and elder-care facilities. There you see everything you dread to become — the silent somnambulists, and the ones who sit laughing to themselves or sobbing heartbrokenly an hour at a time, and those who seem terrified by what you can’t see and are beyond comfort by caregivers. Then there are the sly plotters, stealing and hiding things, vindictively thwarting the nurses, endlessly plotting their escape from locked-down senior living prison.

I’ve seen old people lurking around the elevator trying to memorize the number-code that visitors punched in to call it up. My father-in-law was one of them. He once charged the elevator in a desperate fury and was hauled away by attendants. On another memorable visit, he stalked the halls yelling, “Where’s my acetylene torch?” and threatening to burn the place down.

“Do not go gentle into that good night” could be the motto of a lot of tormented old people.

It is in order to avoid allowing the children to see such upsetting scenes of rage and despair in the grandmother’s behavior that the children are initially told that bedtime is 9:30 PM, and then cautioned not to leave their room after that time. Of course, the weird noises at night and the increasingly strange behavior during the day leads both children to start violating the grandparents’ rules by venturing out of their room after bedtime. Their imaginations immediately leap to horror-film analogies. Is Grandma a werewolf? Is Grandpa an ax-murderer?

And one of the grandmother’s odd quirks draws a clear parallel to the witch in Hansel and Gretel: she keeps requesting that her granddaughter Becca (Olivia DeJonge) help her clean the big roasting oven by climbing entirely inside it, so she can clean the back of it where the grandmother can’t reach. Very reluctantly, the girl complies. Shyamalan then holds on an admirable long shot of the grandmother standing by the oven, staring at the girl’s sneakers barely sticking out of the huge oven, twisting a dishcloth in her hands as if fighting off a terrible impulse to slam the oven door shut and roast her grandchild for dinner.

When the horrors commence, all are related to ordinary everyday horrors of old age. The illnesses of the elderly, that are so frightening because the final, fatal one is anticipated, are represented early on, when Becca peeks out of her room after bedtime and sees her grandmother lurch past the downstairs hallway, vomiting on the floor as she goes. But then, the morning after, all is explained away by the two seemingly nice old people, who are terribly distressed to have the children see such things. Just a touch of the stomach flu, they say.

Incontinence is another of the quotidian horrors on display, in all its grossness and pathos.

The horrors of dementia and old-age depression are the main focus, however. The grandmother in her rocking chair staring at the wall and laughing raucously at nothing — the grandfather (Peter McRobbie) discovered in the barn in a state of poignant loneliness, with his forehead resting on the top of a gun barrel which he swears he was just cleaning — and the way both of the old people walk slowly around the farm as if in a trance, not responding when called, like sleepwalkers or ghosts.

Even the primal horror of the wasted flesh of the very old is wonderfully represented in the scene featuring the grandmother apparently gone mad, naked and clawing at the walls. This results in the boy saying simply, “I’m blind,” after witnessing it.

Reviewer Mark Brunson, dismissing the film by saying it “might as well have been called Old People Are Scary!,” says something more perceptive than he seems to realize. The film is indeed about a particular kind of biological horror: how “old people are scary,” to the uncomprehending child.

The child is such a different animal from the elderly person — they look at each other across a great chasm of time. To a child, the very old person can seem an alarming, crabbed relic of some harsh earlier era, wizened by inconceivably difficult struggles but still up tottering around, speaking an outdated dialect.

I can remember feeling a deep dread of my grandmother when I was a kid. Even though she was generally placid and kind, she seemed strange, scary, and formidable to my childhood self. She’d lived through the Depression as an impoverished tenant farmer — she’d run her drunkard husband off her land with an axe and fought off a vicious dog with a broom handle. The marks were all on her in stark white hair, masses of deep wrinkles, and terrible scars like a thumbnail split in half, where her mother had hacked at her with a knife in a fit of rage during her own harrowing American Gothic childhood.

She seemed capable of any ferocity.

Of course, old people are also scary to the all-too-comprehending adult. The very old are shortly going where we don’t want to go ourselves, just far enough ahead of us to convey the terror and the mystery of it vividly on their bodies. The whitening hair, the loss of pigment in the papery thin skin, the gnarling of the hands, the stooping and thinning and shrinking as their bodies seem to visibly withdraw from the world, turn living people into ghostly presences. The way their gazes begin to drift to the horizon, or recede inward, and their thoughts return to the lost past in long, meandering recitations, are all representing the experiences of the last mental and physical transformations leading to death.

If that ain’t good material for a horror film, I don’t know what is. But as timely as Shyamalan’s “caregiver horror” film is, it’s also a high-risk variation on the genre. How many spectators want to be frightened by something so hauntingly close to home?