Newlyweds Nathalie and George fly to a remote island retreat off the coast of Maine for a quiet vacation, hoping to escape the noise of everyday life. The secluded beach house is looked after by Lance, a longtime acquaintance of Nathalie who knows the place inside out. George, wanting to bond, heads out for an overnight fishing trip with Lance, giving the two men a chance to talk and understand each other better while Nathalie enjoys a rare moment of solitude.
But the relative peace is upended when Kent arrives unannounced, the ex-boyfriend of Nathalie. Kent explains that his girlfriend Evelyn has left him because of his drinking, and not long after, he helps himself to a bottle of vodka. While Nathalie is away, he makes a bold pass at her, drinking straight from the bottle and leaving the room in a drunken haze. The party ends with Kent collapsing on Nathalie’s bed, and she returns to find him dead—seemingly the victim of alcohol poisoning.
Panicked, Nathalie hides Kent’s naked body in the cellar beneath the dining room. When George returns from the fishing trip, she tries to maintain composure and pretend nothing is wrong, but the situation quickly spirals. George notices the cellar door under the dining table isn’t fully closed and takes steps to fix the problem. He also discovers lingering signs of Kent’s visit—the flowers and chocolate Kent had given Nathalie—and she confesses that Kent did come by. She admits she deposited his body in the cellar, hoping to keep the secret.
The couple debates their next move, torn between fear, embarrassment, and the fact that Kent’s clothes are missing while his neck bears the marks of the earlier disturbance. As a prominent judge, George feels the weight of a possible investigation, and Nathalie’s past struggles with pills complicate their judgment. They ultimately consider disposing of the body at sea, binding Kent to an old stove and dragging him toward the water, when Lance unexpectedly returns, forcing them to rethink their plan. They retreat to the house, trying to appear calm as they begin to reconstruct what happened.
Back inside, George uncovers a shocking detail: Kent’s bottle was not ethyl alcohol at all but methanol, a poisonous substance. The combination of Kent’s heart problems and the tainted drink explains the tragedy. Nathalie, shaken, goes for a swim to clear her head, hoping to regain some perspective.
When she returns, she notices Kent’s white linen suit drying on Lance’s porch and plans to have it cleaned. She heads to find George to share the good news, only to find him on the veranda, where the truth of Kent’s fate has taken a darker turn—George has already embedded Kent’s dismembered body into the concrete steps. Horrified, Nathalie tries to run, but George captures her, ties her, and drags her back inside, where he imposes a harsher form of punishment.
Seeking help, Nathalie finds Lance and explains everything, including Lance’s own innocence in the matter. A missing postcard Kent had sent is found in Lance’s house, and Lance reveals he meant to pass it along but forgot. Confronted with the possibility that Lance might be involved, Nathalie grows desperate. Lance maintains his innocence and follows Nathalie toward the beach as tensions flare between him and George. George shoots Lance, forcing Nathalie to flee once more.
Nathalie is captured again and is restrained as George, who’s drinking heavily all the while, begins to cement her legs in a metal container. The tables turn when George staggeringly loses his balance, claims he cannot see, and collapses from the veranda, impaled by a spire. Nathalie tumbles into the water, unable to surface because her legs are bound, and a passing beach patrol boat finally spots her, rescuing her from a fate she narrowly escaped.
Back aboard the boat, Nathalie recounts her ordeal to the patrolman as they drift away. He asks for a drink, and she instructs him to check the cooler under his seat. Unbeknownst to her, George had slipped some of Nathalie’s medication into the water bottle, leaving the patrolman unaware of the danger he is about to drink, and closing this harrowing tale with a chilling reminder of how thin the line between survival and peril can be on a remote island.
