Ben is a 39-year-old orthopedic surgeon from Jacksonville, Florida, specializing in treating young athletes. He is an avid hiker and former high school track star with a clinical, logical mindset that serves him well in emergencies. Stranded in the remote Utah wilderness following a plane crash, he uses his medical expertise and survival skills to care for his fellow passenger while recording ongoing messages to his wife.

Ashley is a 34-year-old magazine columnist from Atlanta, Georgia, traveling home for her upcoming wedding rehearsal dinner. A former state-level taekwondo champion, she possesses significant physical and mental fortitude. Despite suffering severe injuries in the plane crash, she relies on her strong sense of humor to cope with the trauma and extreme conditions.

Rachel is Ben's wife and high school sweetheart. A former cross-country runner, she shares Ben's love for the sport but approaches it as a joyful activity rather than a strict competition. She is a grounding force in Ben's life. Her presence is heavily felt in the wilderness through the compass she gave him and the ongoing recordings he addresses to her.

Grover is a seasoned private charter pilot with over 20,000 flying hours. He frequently flies unrecorded routes over the High Uintas Wilderness, enjoying the freedom to fly low and bypass standard regulations. He is a dedicated family man who speaks fondly of his long marriage, though his casual approach to his health has sudden consequences.

Vince is Ashley's fiancé, waiting for her to return to Atlanta. He lives in a clean bachelor penthouse and owns a Mercedes, offering Ashley a comfortable and stable life, though she internally questions whether they are a perfect match.

Gayle is Grover's wife of many years and the mother of their five children. Grover views their marriage as the greatest source of happiness in his life, offering her as an example of enduring love.

Tank is Grover's small Jack Russell terrier who serves as his frequent copilot. After the crash, Ben and Ashley temporarily rename him Napolean because he acts much tougher than his small size suggests, bravely defending their campsite from wild animals.