After a late start, Josh guides Kaia’s raft through the dangerous Devil’s Stairs rapids. The exhilarating experience lifts everyone’s spirits, and the group stops for lunch and a bathroom break. As some of the guests talk about their families, Kaia shares a story about her late husband, Parker. Later, she sees hawks or eagles circling above the canyon and experiences a painful internal flashback to his final moments trapped in a cave, where he promised to come back to her as a hawk. The memory of his death leaves her shaken. The group soon returns to the river to tackle the next rapid, Marble Creek. As they enter the whitewater, their entire supply of potable water topples from Macy’s gear raft and falls into the river.

Everyone stops rowing to look at the falling jugs, causing the raft to spin sideways and be hit by the next wave, throwing Kaia and several other women into the rapids. Trapped briefly under the boat, Kaia panics, the feeling of being stuck in the dark reminding her of her husband Parker’s death.

After her life jacket brings her to the surface, she is battered by rocks and pulled by the current. She remembers Josh’s instructions to get into the “Idaho Easy Chair” position—floating feet-first downstream—which allows her to navigate the rest of the rapid safely. Bryan pulls her into his raft. The guides confirm that the water jugs are broken and their contents lost. With only the water in their personal bottles, the group must now ration their supply until they can boil more at that night’s camp.

The group arrives at the Camas Creek campsite after dark, feeling cold, thirsty, and exhausted. The mood is tense as the guides remind everyone not to drink untreated river water due to the risk of pathogens like Giardia, a warning made more urgent by the fact that several guests are already suffering from stomach issues after lunch. Josh instructs Bryan to boil water before setting up the groover, and Kaia snaps at Josh, angry at the guides’ abuse of Bryan.

Kaia thinks of a miserable but ultimately bonding experience she shared with Parker in Nashville, when a concert was cancelled at the last minute due to weather, forcing them to walk for hours back to their hotel in a downpour. Realizing she must take initiative, she volunteers to help boil water. Her action defuses the tension, and the other women, led by Deborah, begin helping to set up camp. After dinner, just as people are preparing for bed, Allie and Nikki begin crying again, terrified of camping at the site of the infamous Camas Creek murders. Josh calmly reassures them that the killer is long dead and that the best thing for everyone is to rest.

An excerpt from Backcountry River Running: A Primer states that certain locations along the Middle Fork are known to possess a “heaviness.” This is described as a sense of unease that is reported by both river guides and their passengers. The text specifically highlights Camas Creek as a frequently mentioned example of such a location.

Kaia, struggling with grief, has a nightmare about failing to save a dying fish. She is jolted awake by a scream from the campsite. Believing it to be another nightmare from Allie, she exits her tent just as Pam discovers the body of Gracie. As Pam screams that Gracie is dead, a nearby guest tent collapses amid the sounds of a stabbing. In the ensuing panic, the campers flee for the rafts, and Pam shoves Kaia, leaving her behind. Kaia attempts to sneak away but sees a figure emerge from the bloodied, collapsed tent. She bolts but trips and falls. A man in Chacos approaches, and convinced she is about to be killed, the narrator strikes his leg with her water bottle.

Before the man can react, a second figure tackles him, and the two begin fighting in the nearby brush. A voice Kaia believes is Bryan’s yells for her to get to the rafts, claiming he has the attacker pinned. She hears Josh roar a threat, followed by the sounds of stabbing and a scream of pain. Bryan begs for help, and Kaia, believing he is fighting Josh to save her, feels compelled to assist him.

She sees one of the men go still. The other man rises, and in the dark, Kaia hesitates, calling out twice before recognizing him as Bryan; Josh lies motionless on the ground. She approaches Bryan, who is holding two bloody knives. He claims Josh stabbed him and that he is about to pass out. As Kaia supports him, she yells for the others, who are already launching the rafts, to come back. She tells them Bryan is hurt and that Josh is the attacker and is now dead. As one of the rafts returns, Kaia notices that Bryan’s labored breathing has become calm and steady. He is still clutching both knives, and a cold smile spreads across his face.

Kaia takes a step back from Bryan as she realizes with horror that he is the killer. He murdered Gracie and the woman in the guest tent. He only kept Kaia alive to lure the others back to shore. Bryan swings a knife at Kaia before the returning women reach shore.

She dodges the attack and screams for the others to run, warning them that Bryan is the killer. As Bryan lunges at her again, Josh—battered and bleeding but still alive—tackles him from the shadows, telling Kaia to escape to the rafts. Bryan quickly overpowers the injured Josh, looks directly at Kaia, and drives a blade into Josh’s throat, killing him. Kaia makes it to the water, where the two rafts are already far from shore. Macy orders the women in her raft to return for Kaia, and they pull her aboard as they see Bryan struggling to launch one of the small, normally unmanned gear boats in pursuit. There are only five people on the raft—Kaia, Macy, Allie, Pam, and Deborah. Any other survivors are on the other raft, which is further downriver, approaching the treacherous Anvil Falls. Macy is confident that the inexperienced Bryan won’t make it past the falls, but she notes that neither will the other raft unless they can catch up and help. Macy is now the only guide.

An excerpt from The River Guide’s Almanac explains that when navigating extremely dangerous Class IV or V rapids, the margin for error is nearly nonexistent: A single misstep, such as a missed paddle stroke or a brief hesitation, can be the deciding factor between a successful run and a catastrophic outcome.

As their two rafts approach the treacherous Anvil Falls, Macy tries to shout navigating instructions to the overloaded, struggling raft ahead of them. With Bryan’s raft in pursuit, both groups enter the dangerous whitewater. Kaia, recalling a dream in which Parker guided her to safety through the earlier rapids, focuses on rowing with all her might. Macy expertly guides them through a series of massive waves, but the first raft nearly capsizes after clipping a submerged boulder. Miraculously, both rafts avoid flipping and make it through the most difficult part of the canyon. Just as they near the exit, believing they are about to escape, Kaia sees something glint on the canyon wall and hears her deceased husband’s voice in her head warning her to get down. Immediately after, the women in the first raft are violently jerked from their boat as it clears the final drop, revealing a trap.

As the first raft navigates the final, steep drop of Anvil Falls, the women inside are violently thrown backward one by one, their bodies falling into the churn as blood sprays into the air. Kaia hears Parker’s voice telling her to remember what happened to his friend, Raymond. The memory comes back: Raymond was nearly killed, and his brother was decapitated by a wire trap strung across a trail.

Kaia looks ahead and sees a thin, glinting wire stretched between the canyon walls at neck height. She realizes that the same thing must have happened to those who initially escaped the scene of the original Camas Creek murders—explaining the gruesome injuries of those found downriver from the campsite. Urged on by Parker’s voice, a phenomenon she recognizes as Third Man Syndrome, Kaia screams for everyone in her raft to get down. The women drop to the floor just as the boat surges upward. Macy, at the stern, does not duck in time; she screams and is swept into the water. Her guide oars splinter against the canyon walls and are lost. The four survivors—Kaia, Allie, Pam, and Deborah—are left floating in a boat with no guide oars. They find the other raft, but no one in it is alive. They soon find the body of Allie’s friend, Nikki, floating face down in the water; when they roll her over, the corners of her mouth are sliced into a grotesque smile.

In the calm water after the falls, the four survivors search for anyone who might have survived the wire trap, knowing Bryan will soon emerge from the rapids behind them. They recover the bodies of five more women—Kerry, Sydney, Yvonne, Teia, and Deborah’s sister, Beth. All the victims have catastrophic injuries to their heads, necks, and arms.

A grief-stricken Deborah tries to pull Beth’s nearly decapitated body into their raft, but Pam convinces her that they must leave the dead behind if they want to survive. Just as they resolve to flee, Bryan’s gear raft appears at the end of the falls. He begins whistling a calm, meandering tune as he rows steadily toward them. Kaia takes charge, and the four women paddle frantically downriver. Their escape is interrupted when they hear a faint cry for help and spot a survivor clinging to a submerged tree.

The River Guide’s Almanac warns against navigating a river at night, a practice referred to as “night running.” The text explicitly states this is not recommended on any part of a river, but it is particularly dangerous in rapids rated Class-Three or higher. The reasons provided are that nighttime conditions compromise visibility, reduce a person’s reaction time, and make rescue efforts substantially more difficult.

The group in the raft races to rescue a fifth survivor, a woman snagged on a tree branch in the rapids, knowing they only have one chance as Bryan closes in behind them. The woman, Imani, reveals that her life jacket is caught and she is too injured to swim. Kaia hears Parker’s voice, and on his advice she tells Imani to unbuckle the vest. As they draw alongside, they see that Imani’s left arm has been severed at the elbow. She manages to free herself just as the raft passes, and Deborah pulls her aboard. Pam, a veterinarian, applies a tourniquet to the stump.

Bryan, now only twenty yards away, applauds them slowly and taunts them about the dangerous rapid ahead. The narrator realizes Bryan is too young to be the original killer, Kellen Stroop, and must be a copycat. Facing the treacherous whitewater with no guide, the group panics over which path to take. As Bryan forces their decision by approaching aggressively, Parker’s voice urges the narrator to look at him for a clue.