A violent inmate, whose face is not shown, escapes from a state mental facility, drowns a man on a private beach, and steals his work uniform.
Five young women reunite for their 5-year college reunion at an exclusive cottage on an isolated island that has no phone contact with the mainland. The setting feels calm at first, but the group carries personal issues and tensions beneath their surfaces, hinting at storms to come.
Meeker is the captain of the small boat that transports the women to the island. Michael Wylie Robert Conrad is the island’s caretaker, and the two men clash with the women both in public and behind closed doors, setting up a tense dynamic that will color every move on the island.
The next morning, the island’s dog is found dead, a grim omen that something is seriously wrong. Later that day, four of the women return from the beach to discover that the fifth has been strangled to death. A flicker of fear spreads through the group as they begin to suspect either Meeker or Wylie, and the question of who fled the crime scene becomes a pivotal point of their perilous night.
The women decide to sail off or at least use the boat’s radio for help, but as they approach the vessel, it explodes in a blast that shatters their plan and tightens the circle of danger around them.
In response, the four lock the men out of the cottage and vow not to leave each other alone for the rest of the night. Through the locked door, the men insist they don’t know anything about the death, while promising that a supply boat will arrive in the morning. The women gather in the cottage and discuss which of the two men might be the killer, weighing motive and opportunity with growing paranoia.
Inside the company cabin, the two men become aware of each other’s suspicions and resolve not to let the other out of sight. They speculate that someone else could be on the island, a possibility that raises the stakes and feeds the unease. Later, Meeker asks to go outside for some air, and when Wylie tries to intervene, a fight erupts. Meeker overpowers Wylie and escapes into the night, leaving both men battered and wary of what comes next.
The following morning brings a confrontation that cracks the façade: Wylie is revealed to be the murderer. He kills Meeker and then tries to convince the women that Meeker caused the tragedy and that he, Wylie, is the one protecting them now. The group is left to decide whom to trust as the supply boat is expected to arrive.
When the expected boat nears, one woman goes to thank Wylie for his alleged help, while the others wander the beach and discover the dead body of the man who drowned earlier. An identifying bracelet reveals his name is Wylie, and the women realize that the man they have known as Wylie is actually an impostor and the real killer. They hurry to warn their friend and each other of the growing danger.
One lone woman, still talking with Wylie, suddenly grasps that he is unbalanced. As three other women approach calling her name, she runs, but he pursues, choking her. The group, initially fearful of getting too close, intervene and strike Wylie with a rock, killing him. Gasping and shaken, they rally and make their way toward the island’s pier, now bound together by a difficult truth and a renewed resolve to escape the nightmare they faced together.
