It’s clear that something is not quite right from the moment that Randall (Noah Le Gros) and Emily (Liana Liberato) arrive at Randall’s dad’s beach house in a small, secluded East Coast seaside town during the off-season. But The Beach House writer-director Jeffrey A. Brown takes his time revealing what kind of danger the young couple is actually in, hinting at a few different horror-movie scenarios before revealing the full-on terrors the characters are facing. That makes The Beach House a bit slow to start before suddenly careening head-first into its nightmare scenario. But the methodical building of tension is mostly effective, and the gross-out horrors of the second half are viscerally unnerving.

The relationship between college students Randall and Emily is under some mostly unspecified strain after Randall left school for reasons that are never made clear. The weekend at the beach is meant to help them restart their romance, but while Randall was under the impression that the house would be empty, soon after they arrive they discover that his dad’s friends Mitch (Jake Weber) and Jane (Maryann Nagel) are also staying at the house for the weekend. Mitch and Jane are friendly and understanding, inviting the younger couple to stay at the house with them since there’s plenty of room, and to join them for dinner, which Randall and Emily warily accept.

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Brown opens the movie with ominous shots of bubbling and gurgling in the surrounding ocean, and something is off about the empty town and about Mitch and Jane themselves, who are simultaneously too friendly and rudely secretive. What is the purpose of their medicine cabinet full of pills? Are they really there as guests of Randall’s dad, whom Randall hasn’t spoken to in a few months? Is Mitch getting a little too friendly with Emily as they chat on the porch? Just why did Randall leave school? There’s a lot of potential for the interactions among the core foursome to turn dangerous, and that’s before Randall breaks out a cannabis edible that he brought along, offering to share with everyone.

The Beach House could be a story about sinister strangers who pretend to be old friends, it could be a story about long-buried family secrets or it could just be the story of a really bad drug trip. Brown teases all those angles during the movie’s first half, setting the audience on edge with jarring music and shots of the beautiful but empty landscape around the house. When a strange fog rolls in and Jane discovers mysterious bioluminescent organisms on the plants and trees surrounding the house, it starts to become clear that the actual threat here is something otherworldly. Emily’s talk about her interest in studying astrobiology in grad school is the key bit of foreshadowing for a second half that rivals Richard Stanley’s recent Color Out of Space for unsettling Lovecraftian horror.

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Whatever restraint Brown exhibited in the first half, he makes up for in the second with some disgustingly horrific moments, including Emily performing impromptu surgery on her own foot with a knife and a pair of tongs, to extract a particularly persistent parasite. Working with the same limited locations and small cast, Brown creates a sense of burgeoning worldwide contamination, while he focuses in on the determination and resourcefulness of his main characters. Whether she’s cutting into her own foot or getting herself and Randall to a makeshift, temporary shelter, Emily draws on an unexpected well of inner strength.

Liberato shows that quiet defiance from the start, as Emily questions Randall’s motives for the trip and expresses her uncertainty about the viability of their relationship. But this isn’t Midsommar and the growing horrors don’t empower Emily to take revenge on a feckless partner. Everyone here is a victim of the implacable threat slowly expanding across the town (and, it’s implied, the world), and Emily does everything she can to save the boyfriend she seemed to be on the verge of dumping. Liberato gets across those complex emotions even while fleeing from deadly ancient parasites, keeping the movie grounded as it gets increasingly nasty in its final act.

A lot of the hints at character development from the first half (especially from Mitch and Jane) don’t quite pay off, and the deliberate pacing can feel a bit like stalling tactics before Brown gets to the good (as in horrifying) stuff. But that stuff is genuinely horrifying, and Brown plays with horror-movie expectations as Emily heads into a dark basement for supplies or sees something crawl past her out of the corner of her eye.

Brown creates an instinctive sense of revulsion at what Emily witnesses thanks to judicious use of special effects, and he sustains a feeling of dread mostly with just fog and eerie lighting (at one point during the drug trip, the screen distorts to resemble the red-and-blue color scheme of vintage 3D). The characters are isolated and alone, but the horror is everywhere.

Starring Liana Liberato, Noah Le Gros, Jake Weber and Maryann Nagel, The Beach House premieres Thursday July 9 on Shudder.

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