Emily and Randall arrive at Randall's parents' beach house, tucked away in a remote vacation town that feels almost eerily empty. The house is roomy and comfortable, and at first the desolate streets and deserted shoreline bring a strange sense of calm. As night falls, the couple settles into their own space upstairs, sharing a quiet moment that swiftly gives way to a small argument—the kind that lingers before fading into the quiet rhythm of a getaway.
The mood shifts when they discover that another couple, Mitch and Jane Turner, are already staying in the same house. Randall's father knew them; old friends visiting for one last chance at happiness for Jane, who is terminally ill. With the upstairs and downstairs options, the four of them decide to share the home for the duration of the visit, creating an imperfect but functional household in close quarters.
Over dinner, Randall pulls out a bottle of edible marijuana, proposing that the group sample it together. Jane and Mitch agree, and the conversation grows warmer as the shared meal dissolves into laughter and tentative affection. The effects blend with the night air, and a strange, shimmering mood settles over the group. Mitch is the first to notice something off—an unusual texture to the water and a faint, unfamiliar glow in the trees and on the surface of the sea. The beach appears alive in a way it never did before.
As the high intensifies, Jane rises to observe the spectacle more closely, though she soon coughs and grows disoriented as a dense fog begins to creep across the landscape. Emily follows the others’ curiosity, but the fog proves disorienting to everyone. Jane eventually retreats, and Emily awakens later to find Jane in the kitchen, catatonic and marked by skin lesions, while Mitch has vanished without a trace.
The next morning, the beach is completely deserted, a startling silence hanging in the air. Randall wanders to the shore, only to return moments later with a pale, sickly look and a disturbed, queasy stomach. In the bathroom, the sink’s water ripples and forms strange patterns, a small prelude to the larger, creeping transformation hanging over the town. Jane moans in the distance, and when Emily goes to help, she discovers that Mitch is missing. On the sand, Mitch reappears briefly, his tone philosophical as he mutters that something is wrong about the place. He steps toward the water and then calmly drowns himself. Emily, trying to escape the sense of foreboding, steps on a washed-up Portuguese man o’ war and feels a sting that triggers a startling image—a worm-like creature writhing beneath an open wound.
With the fog thickening, Emily manages to reach the house and discovers Randall having fallen into a more dangerous, feverish state. Jane, now with milky white eyes and a strange discharge at her mouth, stalks him through the hall. Emily and Randall barricade themselves inside, trying to keep Jane at bay as the fog closes in around them.
Night deepens, and the fog becomes a living thing, curling around the houses and choking the air. Emily finds a police car with a working radio and a voice that warns of exposure and urges barricades, coupled with the instruction not to breathe the fog. A beacon of hope appears in the form of a survival instinct: Emily spots a basement full of scuba gear and oxygen tanks, a critical lifeline for breathable air in the contaminated environment. She also makes a grim discovery—a mutated person feeding on a corpse upstairs, a sign of the infection spreading through the town.
Randall succumbs to the infection in a chilling progression, vomiting a squid-like creature before his eyes turn white and his body fails. Emily, driven by a will to live, retrieves the scuba gear and returns to confront Randall, who lunges at her. In self-defense, she strikes him with a scuba tank and escapes into the night once she has the keys to a car. The fog makes her disoriented, and a desperate drive ends in a crash. She stumbles from the wreck into a tidal pool, the fog pressing in around her as she breathes in the tainted air and battles vivid hallucinations of the microbe-filled water she just escaped.
The morning light reveals a fragile calm over the shoreline, but Emily is not safe. She lies on the beach, trying to steady herself and cling to the promise of survival, even as the infection works its way through her. A powerful, final wave surges over her body and drags her out to sea, leaving her fate uncertain but the town already lost to a silent, creeping terror. The scene lingers on the edge of memory and the unknown, a stark reminder of how quickly a quiet coastal escape can become a fight for life.
