Are you afraid of the dark? If so, Ari Aster’s debut movie, last year’s Hereditary, may have been too much to take. Its tale of familial dysfunction and repressed trauma was enriched by its gloomy color palette, taking place mostly inside a badly-lit home or outside, at night. Now Aster returns with Midsommar, which couldn’t be more different: Its action occurs under the unsparing, perpetual daylight of a Scandinavian summer. But sunshine can be crueler than the dark, because there is nowhere to hide.

The movie begins in snowbound America, where we meet our heroine Dani (Florence Pugh). She’s a sweet-faced college student, traumatized by a terrible family tragedy. She clings to a callous boyfriend named Christian (Jack Reynor), who is more interested in hanging out with his gang of grad school mates, including a Swede named Pelle. Christian wants to dump her but feels guilty about it—it’s a toxic dynamic, and the dread starts to build. The boys have a trip to rural Sweden planned, where they will visit Pelle’s home. He comes from a close-knit community, he explains, that is about to throw a once-every-90-years midsummer festival. Dani tags along out of lonely desperation.

Courtesy of A24

A bizarre scene lies before the Americans. Delighted to be among the Swedish tribe at last, they accept the odd food offered them and revel in the sunshine. The Swedes are all dressed in white garb and prone to bursting into traditional song and dance. The fictional tribe’s customs owe a lot to actual Swedish tradition—the white dresses and floral headdresses of the real Midsommar festival are authentic—but their eccentric beliefs toe the line between religiosity and spookiness. They practice an inscrutable independent religion anchored by oracular prophecy, and live in a system of barns that look like they were decorated by an unusually cheerful brotherhood of medieval monks. (Think medieval fresco, but brighter.) The production designer, Henrik Svensson, has built a truly frightening and intricate universe whose iconography is dominated by symmetry.

The Americans find it all fascinating. But as the tribe gets weirder, the Americans start to misbehave. Their manners are awful, and the nastiest of them, a boy named Mark (Will Poulter), accidentally takes a leak on a holy ceremonial tree. Josh (William Jackson Harper) sneaks into the temple at night.

To say more about what follows would be to ruin the plot. Suffice to say that the tribe is preparing for a traditional northern European–style fertility festival, complete with a girl crowned the May Queen. Because all this is framed by the movie’s tragic overture, Dani’s unresolved pain becomes intertwined with the strange proceedings. Amid all this confusing stimulus she tries to simply keep going, one foot in front of the other, day by day. But under the vicious glare of the Scandinavian sun something seems to shake loose inside Dani, as if she has some special affinity with the ritual magic of Pelle’s tribe. As the fertility rites begin to pick up pace, the relationships between the American tourists start to shift. Something, or someone, is about to change.