Sage and Diego arrive at a sprawling lakeside country house they’ve rented for the weekend, hoping to celebrate a moment before Diego dives into a new writing project and Sage continues the editing work that supports him. The mood is hopeful, a quiet mix of anticipation and companionship, until the doorbell reveals an unexpected guest: another couple, Will and Cin, who also booked the same house. The reality of the double-booking forces the four to improvise, and they agree to share the space for the weekend, turning what should have been a private retreat into a shared, overlapping stay.
The first day is spent in the sun and water around Bone Lake, with the four friends drifting between swims and meals as they negotiate space, boundaries, and a growing sense of moodiness beneath the surface. Will spins a chilling history—an unknown serial killer who used the lake as a dumping ground since the 1950s—adding an unnerving current to their otherwise relaxed afternoon. As the day wears on, flirtations creep in: Cin and Will test limits as they make provocative advances toward Diego and Sage, while Diego quietly guards a more personal secret—he intends to propose to Sage over the weekend, presenting a grandmother’s wedding ring as a symbol of their future—an idea that seems to surprise and unsettle them all in equal measure.
That night, the curiosity of the group turns toward discovery. Will and Cin lead them to a set of locked rooms within the house, exposing a disturbing contrast between their casual surface and the concealed, darker games beneath. One room reveals a stash of sex toys and a swing, a visual reminder of the couples’ private fantasies; another hides a Ouija board and a collection of newspaper clippings about disappearances around the lake, hinting at something older and more dangerous than a simple party game. The atmosphere grows heavier as the line between play and danger blurs, and the house itself seems to press in with secrets and old whispers.
The next morning breaks with tension and revelation. Will unexpectedly proposes to Cin using Diego’s grandmother’s ring, a dramatic gesture that shocks Diego and triggers a private confrontation. Will’s apology comes with a confession that he believes Cin is cheating, and Diego’s response is sharp and honest: Sage once betrayed him early in their relationship, and he understands the fragility of trust between them. Will promises to return the stolen ring by weekend’s end, but the tension lingers like a fuse waiting to ignite. A trip into town for groceries becomes another revelation, as Will shares a startling claim that Diego told him Sage had been caught masturbating in the bathtub, casting Diego’s practical dream of their partnership in a doubt-filled light. The couple’s chemistry strains under the weight of suspicion and fear, and Cin’s persistent pursuit of Diego presses hard against Sage’s resolve.
As night falls again, Cin propositions Sage to take molly together, a temptation Sage initially accepts but then confesses that the drug was a ruse she used to gauge Will and Cin’s manipulation. The mood shifts from uneasy curiosity to a desperate urge to escape. The plan to leave is thwarted when their electric car won’t cooperate: the charger has been removed, and the battery now only carries them a few miles. The tension erupts into violent confrontation as Will claims to have slept with Sage—an accusation she denies—and Diego tries to back the car out of the driveway, only to be struck by Cin in her own vehicle, throwing the weekend into a nightmare.
Sage and Diego awaken not in safety but bound with duct tape, confronted by the stark truth of Will and Cin’s identity as Thomas and Alice Price, siblings from a powerful publishing family. As teenagers they had an incestuous relationship and murdered their parents, and since then they have terrorized six other couples at their family estate, using psychological mind games to test the strength of relationships before driving them to ruin or murder. The horror of their control becomes brutally clear as Sage and Diego attempt to flee. Cin chases Sage with a butcher knife, and Sage manages to strike Cin with a glass, a shallow cut marking the first tangible resistance in a nightmarish game. Will pursues, while Diego hides near the boat dock and violently secures Cin by stabbing her through the foot, trapping her against the terrain.
A new, brutal weapon enters the scene as Will—now armed with an electric chainsaw—advances toward Diego. In a decisive moment, Sage raises the axe and strikes Will in the head, ending his threat. The couple’s flight resumes, this time aboard a boat, but Cin ambushes them once more. Diego retaliates by striking Cin’s hand with the axe, crippling her grip and fingers, and Cin slips into the lake, her hair snagging on the boat’s propeller. Sage maneuvers the craft, forcing Cin’s fate to spin toward the propeller, ending her threat in a brutal, fatal moment.
With the killer siblings subdued, Sage and Diego drift away aboard the watercraft, discovering a final, eerie calm as they float. Diego retrieves the grandmother’s ring from Cin’s severed finger and, in a moment of dark humor and renewed faith in their bond, proposes to Sage once more. They share a long, uneasy laugh that dissolves into a tense, silent stare into the distance, a poignant ending that lingers longer than the weekend itself.
