Hannah falls asleep and has a nightmare in which Captain Keith appears and warns her that the jungle will claim her. A panther lunges from the trees, and she wakes screaming at sunrise.

She discovers that their mesh bag—containing all remaining food, their water bottle, a phone, and the first-aid kit—is gone. Jackson guesses that an animal took it, drawn by the tuna scent.

They go into the jungle for drier wood, and with Jackson coaching her, Hannah lights a fire for the first time. She adds green branches to produce heavy smoke and scrawls the word “HELP” in the sand, lining each letter with dark rocks.

She asks Jackson to look for food while she tends Emmy’s worsening, deep wound with exposed bone at a nearby stream. She then hikes both ends of the beach searching for help: One end terminates at a stone outcropping overlooking a deserted inlet, while the other stretches in an empty line for miles. She concludes that staying put is their best option. The nearby fruit trees have been stripped clean, leaving only three guavas. Back at camp, the incoming tide has extinguished the fire. She rebuilds it farther from the water. Jackson urges her to check Emmy, who has relapsed into high fever with a ruptured, foul-smelling wound. Hannah cleans it at the stream and returns Emmy to the raft. Emmy briefly murmurs “Ben” before losing consciousness. As Hannah finally attempts to rest, she hears a helicopter.

Hannah leaps up and waves the helicopter down as it passes overhead—but when she turns to show Jackson, the sky is empty. The helicopter was a hallucination, brought on, Jackson suggests, by extreme exhaustion, dehydration, and hunger. Hannah is shaken by her inability to tell what is real. She remains unable to sleep, and Jackson keeps a close eye on her throughout the day.

That night, she sits alone by the fire, unable to shake the feeling she’s missing something important. A branch snaps, and she spots a figure pacing deliberately inside the tree line. She slips away from the firelight, circles through the jungle, and watches as a man steps out of the shadows, punctures the raft in three places, kicks sand onto the fire, and disappears. Hannah gives chase but loses him in the dark.

The deflated raft and the damage to the fire prove that she didn’t imagine it. Jackson questions why an intruder would only damage the raft rather than attack them directly. When he suggests that she may have hallucinated again, she rejects this with anger. He comforts her, and Hannah remains convinced that someone is still watching them from the jungle.

At dawn, Hannah feeds armfuls of green branches into the fire until a dense column of smoke climbs into the sky. She refuses Jackson’s repeated urging to rest, sending him to forage while she tends the fire and checks on Emmy.

When Hannah enters the jungle for more branches, the forest goes abruptly quiet. She spots a flash of bare skin and gives chase, following the figure through dense brush before losing him. She then kicks her own sticker-covered water bottle underfoot, one of the stolen items.

The chase leads her to a crude shelter. Her mesh bag hangs from a branch; the first-aid kit and phone pouch are intact, though the sunscreen is gone. The stolen food cans lie smashed open, and a massive pile of fruit—apparently gathered from every tree near camp—is heaped nearby. Someone has been deliberately stripping the area, making survival more difficult for them.

As she turns to leave, she notices a white button-down shirt inside the shelter that she recognizes. Before the realization fully forms, a branch swings at her head from behind.

Hannah dodges the blow but slams her head on the ground. Ben stands over her, battered but alive. He confirms that the boat’s emergency flotation ring kept him from drowning.

When she confronts him about the theft and sabotage, he confirms it. His plan was to be the sole survivor and frame Captain Keith for the disaster. Hannah’s smoke signal has forced him to act before rescue arrives.

A prolonged fight unfolds across the beach and jungle. Hannah throws sand in his face and flees, but Ben catches her, pulls her down by the hair, and punches her. She escapes by driving a rock into his temple. He catches her again in the jungle; a fall tears a loose flap of skin from her scalp. At the stone outcropping, Hannah buys time by asking about his plans for Emmy. Ben says that killing her will be regrettable but necessary and promises to memorialize both young women in the story told after their deaths.

When Hannah asks what he will do about Jackson, Ben looks genuinely confused. At that moment, a real helicopter appears, with Hannah’s smoke signal visible nearby. Enraged, Ben drags her toward the cliff’s edge by her hair, above jagged rocks jutting from the surf below. Hannah challenges the logic of his story, and he crouches down and informs her that Jackson isn’t with them because he killed Jackson on the boat.

Ben recounts what happened during the second storm. Jackson had Ben’s knife but used it to tie an unconscious Hannah to the boat to keep her from washing overboard, telling Ben plainly that he wouldn’t survive but Hannah would. While Jackson was focused on securing her, Ben grabbed the knife and stabbed him in the neck. A wave rolled the boat; Ben blacked out and woke up alone in the ocean.

Hannah’s denial collapses when she recalls the flotation ring propped at Ben’s camp. Replaying every moment since the beach, she understands: Jackson never physically touched anything; refused every offer of food, water, and sunscreen; and consistently addressed her as “you” rather than “we.” As the inconsistencies fall into place, she begins reinterpreting the days that followed the storm.

When Ben grabs her by the throat, Hannah remembers Jackson urging her not to quit and wraps her legs around his, grabs his ankle, and pulls. He topples backward off the cliff. His scream cuts off when he hits the rocks below, and the surf begins drawing his body out to sea. Hannah vomits and then forces herself back to the beach as a helicopter lands.

While walking, she replays the past days without Jackson in them: only one set of footprints and Emmy lying alone where Hannah had remembered Jackson beside her. Sobbing, she drops beside Emmy just as she stirs. With rescuers spreading across the beach, Hannah tells her they’re going home.

Nearly a year later, Hannah is a student at Linfield University. She receives a travel photo from Emmy, who’s traveling the world. Emmy’s arm infection had been severe enough to nearly cost her the limb, but she recovered and has become a popular travel blogger. Hannah keeps all her social media private, and neither of them has spoken publicly about the ordeal.

Hannah struggles with grief and rarely returns home. Guilt over Jackson’s death makes it difficult for her to face his parents; she had her diploma mailed so that she didn’t have to attend a graduation ceremony held in his memory. Publicly, Ben is regarded as the story’s villain, assumed to have died at sea. Only Hannah and Emmy know that he survived and made it to the island. His body, like Captain Keith’s and Jackson’s, was never recovered.

With the one-year anniversary days away, Hannah is on the phone with her father when Emmy appears on campus—a surprise he helped arrange. Emmy says that she didn’t want either of them to face the anniversary alone and proposes that they spend spring break in Italy rather than attend the somber family memorial, determined not to let Ben continue to influence her plans. Hannah agrees on one condition: no boats. They press their matching, worn friendship bracelets together.