In the viscerally unnerving films of Ari Aster, there's nothing more horrific than the reality of human grief. His haunted-house thriller, Hereditary, followed a family rocked by traumas so devastating that the eventual scenes of devil-worshipping naked boogeymen almost came as a relief. Aster's new movie, Midsommar, doesn't pack quite as terrifying a knockout punch, but it casts its own weirdly hypnotic spell.