The latest from Ari Aster doesn’t quite swerve off into a macabre occult or seasonal cult rite the way “Heredity” (2018) and “Midsommar” (2019) did to the delight of art house horror fans, though “Beau is Afraid” has its own special flourishes of outré that disturb as much as they provoke. The film moves in a very A-then-B fashion with flashbacks to inform us on the trauma unfolding in the present. We begin in the dark with a series of dull thuds and agonized groans. There’s occasional bolts of white light and peers through murky pink filament. What’s going on, you might ask, trench warfare at night? Soon the answer is delivered as Beau is birthed and slapped awake into his new world. We leap ahead to find the mature, balding 40-something Beau (Joaquin Phoenix) in therapy, where we learn he has a lot of mommy issues. Given his father died at the very moment of his conception, this makes sense. His mother calls several times during the session; he doesn’t answer, but tells his therapist (Stephen McKinley Henderson) he’s supposed to go visit her the next day – a task Beau doesn’t fully want to do.

We wander through chaotic streets, or is this unsettled world a projection of Beau’s inner turmoil? A berserk tattoo-faced man chases him with maniacal intent on his way home to a high-rise roost, where he hears news of a naked man stabbing people randomly. That evening, as Beau sleeps, a neighbor keeps sliding notes under his door asking him to turn down the music, yet his apartment is mute, and when Beau takes a bath, another neighbor literally drops in, in nearly the same demonic fashion a possessed soul does in the “Evil Dead” reboot out this week. Getting to mom proves elusive too. Lost keys, lost luggage – he never makes it to the airport, and when he calls his mother a UPS driver (Bill Hader, though you’d never know because you never really see him) answers and blathers on about police on the way and something about a chandelier and a missing head.

Beau remains absurdly calm and tries a plan B. The end result is that he gets stabbed, hit by a car and wakes up two days later in the bucolic home of Roger (Nathan Lane) and Grace (Amy Ryan, so good in “Gone Baby Gone”), kind medical professionals who nurse him back to health. Lurking around is a menacing looking “former war hero” (Denis Ménochet) who I’m not sure ever speaks, and the couple’s surly, sassy daughter (Kylie Rogers), who offers to drive Beau to his mother’s house. It turns out to be something of a blunt-smoking, kangaroo-court shenanigan. 

With effusive control, Aster keeps working us – and Beau – in a downward spiral where the sense of what’s real and what’s not is as murky as that birth canal opener. Lost in the woods, Beau stumbles upon a theater group enacting the play of his life, and there’s a neat segue into animation, further gonzo, dark turns and Parker Posey, superb in a brief yet pivotal part. Mom’s in nearly every frame even when she’s not there, but about midway through we get her in the flesh, in flashbacks (played by Zoe Lister-Jones) and breathing fire in the now (Patti LuPone, bringing it). The line-blurring journey is reminiscent of the award-winning Daniels’ film “Swiss Army Man” (2016), with Aster’s frenetic edginess and dread imbued in nearly every frame. It’s a near three-hour odyssey that rivets right up to the Orwellian finale. Not all of it works, and Beau never seems genuinely afraid at times when others might hit the panic button, but Aster’s film, like his others, has that lingering provocative tease that’s both a sign and a gift.

• At Landmark Kendall Square Cinema, 355 Binney St., and AMC Assembly Row 12, 395 Artisan Way, Assembly Square, Somerville.