Ari Aster can likely cross off “sophomore slump” from his list of many nightmares.

Distributor A24 let loose the follow-up to the director’s widely praised hit debut feature, “Hereditary,” with two buzz screenings, which ran simultaneously in New York and Los Angeles on Tuesday night. Response was almost unanimously positive, if not significantly rattled.

“Holy s—,” wrote Slash Film’s Chris Evangelista, adding that the movie was “disturbing” but an absolute “crowd pleaser.” Dozens of early viewers complimented Aster’s ability to create plausible terror in broad daylight, while others reveled in a leading performance from on-the-verge indie darling Florence Pugh and the deadpan bro antics of her co-star Will Poulter.

“Delightful from its nightmare of an opening to its floral purge of a finale,” said IndieWire’s David Ehrlich.

“I don’t know that I’ve ever felt so gutted and seen by a movie. I felt sick, I felt joy – I felt so much,” commented Nerdist’s Lindsey Romain.

[Warning: minor plot details of “Midsommar” ahead]

“Midsommar” follows a pack of American boys (grad students, seemingly) who trek to rural Sweden to observe and participate in a midsommar season festival — a typically whimsical Northern European custom of ringing in the solstice with organized dances, feasts and flower crowns (long before black SUVs brimming over with stars from the CW would appropriate them for Coachella).

Tensions are high, however, as Christian (Jack Reynor, whose glassy blue eyes get a sinister upgrade through Aster’s lens) has invited his grieving girlfriend Dani (Pugh) to crash the party. Dani and Christian are not only living with an unspeakable trauma she suffers at the top of the film, they’re fighting for dear life as a couple. Christian can’t seem to “get off the fence” about staying together, as one characters says, and his lack of empathy has Dani bending over backwards to maintain the status quo while she mourns.

This particular festival takes place in a peculiar but long-standing communal village, where the gang’s classmate Pelle (newcomer Vilhelm Blomgren) was raised. He serves as their host to increasingly strange traditions. They not only give way to horrors in the angelic, prolonged sunlight of the Swedish solstice, but bring out the worst in their foreign guests and their respective interpersonal beefs.

Aster and members of his ensemble Reynor, Poulter, and Blomgren turned up to Brooklyn’s Alamo Drafthouse Theater to toast the the film. A Q&A was live-streamed to Westwood’s iPic Theater in Los Angeles (where their co-star William Jackson Harper saw the movie for the first time).

“About four years ago, I was actually brought a broad folk horror concept by a Swedish production company called B-Reel. They pitched me an ‘Americans going to Sweden and then getting killed off’ concept,” Aster shared in Brooklyn with moderator Leslye Headland (“Russian Doll,” “Bachelorette”).

“At the time, I was going through a breakup that was fresh. I saw a way of marrying the breakup movie with the folk horror subgenre and making it this big operatic movie. It became very personal,” he said.

Aster, for what it’s worth, said Pugh’s fictional character represented his real life experience. It hits theaters July 3.

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