Jack is a recent Dartmouth College graduate and an experienced wilderness guide who grew up on a ranch in Colorado. He possesses a hard-nosed, pragmatic approach to survival, having learned tough lessons early following the tragic death of his mother in a whitewater accident. He relies heavily on his gut instincts and views nature as beautiful but inherently violent.

Wynn is a gentle giant from Vermont who grew up working on his father's maple-sugar farm. Also a recent Dartmouth graduate, he approaches the world with an idealistic, artistic temperament and strongly believes in the inherent goodness of people. He often creates ephemeral art out of natural objects while waiting at campsites.

Maia is a tough, highly educated geochemist from a wealthy Rhode Island family. She traveled to the subarctic to study how remote bodies of water absorb acid rain. Early in the journey, she goes missing in dense fog, only to be discovered later by Jack and Wynn suffering from blunt-force trauma and severe hypothermia.

Pierre is a scientist in his mid-thirties who is married to Maia. He lacks the wilderness expertise necessary for the remote Canadian environment and travels with a shotgun. When Jack and Wynn first encounter him, he is visibly panicked, claiming his wife vanished into the fog during a bathroom break.

Brent is a portly Texan and former Marine taking a canoe trip with his friend JD. Though he initially appears vulgar and dismissive of the looming forest fire, he is actually highly efficient and capable in the wilderness. He travels with a motorized canoe and a rifle, which he is quick to use to protect his property.

JD is a skinny Texan and former Marine traveling the river with Brent. He is quiet but intense, often consuming large amounts of bourbon at camp. His lingering, silent focus on the injured Maia makes the other characters deeply uncomfortable.

Shane is Jack's father, a Colorado rancher. Following the sudden death of his wife in a river accident, he became emotionally withdrawn and essentially stopped speaking. He taught Jack many practical outdoor skills, including how to reset a dislocated shoulder.

Lloyd is Shane's twin brother and Jack's uncle. Unlike his deeply quiet brother, Lloyd is highly verbal and known for sharing wisdom about life and literature, particularly the idea that a good storyteller must know when not to lie.

Hansie is Wynn's mother, residing in Putney, Vermont. She is a welcoming, warm presence who helped instill Wynn's deep faith in the inherent goodness of the universe.

Jess is Wynn's sister. She looks up to her older brother immensely and strives to follow in his footsteps, sharing his infectious enthusiasm and joy for living.