Kaia is a young widow grieving the unexpected death of her husband, Parker. She attends a five-day women's rafting retreat on the Middle Fork of the Garnet River to honor a trip they originally booked together for their 30th birthdays. Emotionally withdrawn and isolated by her sorrow, she initially struggles to connect with the cheerful guides and other guests. The physical demands of the river gradually force her out of her numbness and back into the present moment.

Leo Marsden is known to true-crime enthusiasts as the sole teenage survivor of the Camas Creek massacre, which occurred seven years ago on the Garnet River. According to official accounts, he survived a killing spree by playing dead beneath his mother's body before fighting back and escaping down the river. His history casts a dark shadow over the current rafting expedition, frequently debated by the guests. He actively follows online discussions about his past.

Allie is a high school librarian and an avid true-crime enthusiast who moderates a popular subreddit dedicated to the Camas Creek murders. Her intense curiosity about the dark history of the Garnet River occasionally alienates the other rafters and frustrates the guides. She packs practically and possesses a surprising background as a former state champion swimmer and softball player.

Macy is a cheerful senior rafting guide for Idaho Rapids Unlimited. She studies recreation therapy at the University of Idaho, believing that outdoor activities can help people heal from trauma. She projects a confident, carefree demeanor to keep the guests comfortable, though she strictly enforces safety rules on the dangerous whitewater.

Deborah is a grounded, pragmatic guest on the women's rafting retreat. She attends the trip as a gift from her daughters following a recent divorce, using the experience to bond with her sister, Beth. She quickly establishes a supportive, motherly presence among the group and easily connects with the other women in her raft.

Pam is a wealthy veterinarian attending the river retreat. Initially perceived as slightly out of place in her designer clothing, she quickly reveals a calm competence and practical medical knowledge. Her professional background equips her to handle stress and injuries with a level-headedness that benefits the entire camp.

Imani is a guest on the women's rafting retreat. She is a devoted mother who frequently speaks of her young twin boys, seeking genuine connection with the other women on the trip. Her warmth and openness help soften the sometimes tense atmosphere among the strangers.

Parker is Kaia's late husband, who died unexpectedly at the age of 28 after becoming trapped in a caving accident. He originally booked the Garnet River trip to celebrate their 30th birthdays. Though physically absent, his memory is a constant presence for Kaia, who frequently imagines his voice offering comfort and tactical advice.

Josh is a charismatic and confident senior guide for Idaho Rapids Unlimited. He projects dominance and expertise on the water, easily commanding the attention of the guests. However, his abrasive leadership style and strict adherence to the company's masculine hierarchy occasionally cause friction with the newer crew members.

Gracie is a capable and upbeat rafting guide who works alongside Macy and Josh. Like Macy, she studies recreation therapy at the University of Idaho and takes her professional responsibilities seriously. She helps set a positive, welcoming tone for the women on the trip.

Beth is a guest on the five-day women's rafting retreat. She shares a close bond and a matching pixie cut with her sister, Deborah, participating in the trip primarily to offer support following Deborah's recent divorce.

Nikki is a guest on the rafting trip and a close companion of Allie. She shares Allie's morbid fascination with true crime and participates eagerly in the campfire discussions about the infamous local massacres, though she is easily frightened by the stories.

Kellen Stroop was a guide for the company Idaho Thrills whose dark legacy hangs over the Garnet River. Seven years prior to the current retreat, he reportedly went on a horrific killing spree at the Camas Creek campsite. His alleged actions remain a popular topic of debate and conspiracy in online true-crime circles.