Peak is a 14-year-old climbing prodigy who was raised in Wyoming and Manhattan. Arrested for illegally tagging a skyscraper with a blue mountain symbol, he avoids juvenile detention by accompanying his estranged father to Mount Everest. He is skilled and impulsive, willing to take extreme risks for the thrill of the ascent. Despite his adventurous exterior, he deeply craves the emotional security of a stable home life.

Josh is Peak's biological father and arguably the best mountaineer in the world. He runs a commercial climbing operation in Nepal and has been largely absent from his son's life for years. Driven by his career and financial pressures, he suddenly orchestrates Peak's release to bring him on a highly publicized Everest expedition.

Sun-jo is a Nepalese boy slightly older than Peak who joins the expedition to Mount Everest. Lacking the socioeconomic advantages of Western tourists, he views the dangerous ascent as an opportunity to secure a better future for his sisters and himself. His natural climbing talent quickly turns him into a rival for the spotlight.

Zopa is an imposing former head Sherpa who has transitioned into life as a Buddhist monk. He acts as a spiritual and practical guide for the Everest expedition, possessing a deep, intuitive knowledge of the mountain's volatile moods. He frequently outsmarts authorities and weather patterns alike.

General Shek is a rigid Chinese military officer monitoring the Everest camps. He actively searches for undocumented climbers and rule violations, threatening to shut down expeditions and imprison locals who attempt to evade his strict regulations.

Patrice and Paula are Peak's six-year-old twin sisters, born on his eighth birthday. They remain in New York while he travels to the Himalayas, representing the safe, unconditional love of his blended family. Their upcoming birthday party serves as a major milestone on Peak's calendar.

Teri is Peak's mother and a former world-record-holding professional climber. She retired from the sport after breaking her back in a fall, choosing to prioritize raising her son over returning to the extreme lifestyle. She reluctantly agrees to let her ex-husband take Peak to Asia to save him from a harsh legal sentence.

Rolf is Peak's stepfather, a lawyer who married Teri after her climbing career ended. Though his relationship with his stepson is somewhat distant, he consistently acts in Peak's best interest and represents the kind of responsible paternal figure entirely absent in the extreme climbing community.

Vincent is an English Literature teacher at Peak's specialized New York school. As an academic mentor figure, he allows his student to complete his school year remotely by writing a cohesive narrative about his journey to Asia.

Holly is an aggressive reporter who originally covered the story of Peak scaling the skyscraper in New York. Suspecting Josh's ulterior motives, she blackmails her way onto the Everest expedition to secure exclusive rights to the young climber's story.

William Blade is a famous actor attempting to climb Everest. He leverages his vast wealth to secure a personal massage therapist from another climber, preferring to hide in his tent rather than mingle with the standard climbing groups.

J.R. is a video producer tasked with documenting the Everest expedition. When the harsh climate affects his subjects, he quickly adapts his coverage to focus on whoever is healthy enough to speak on camera.