Rudi is a small, slim teenager living in the Swiss Alpine village of Kurtal. Despite working as a dishwasher at the Beau Site Hotel, he wants nothing more than to be a mountaineer like his late father. His physical limitations and his family's strict prohibitions frustrate his ambitions. He possesses natural climbing instincts and courage, finding peace only when he leaves the village to explore the glaciers.

Captain Winter is a tall, English mountaineer visiting the Alps to climb the unconquered Citadel. Calm under pressure, he possesses a commanding presence. Unlike the local guides who are bound by village rivalries, Winter approaches the mountain with practical ambition. He recognizes Rudi's potential immediately after the boy helps pull him from a crevasse.

Teo is the 55-year-old cook at the Beau Site Hotel. He was once a great mountaineer but walks with a limp due to the same accident on the Citadel that killed Rudi's father fifteen years earlier. Understanding the irresistible pull of the mountains, Teo risks his own safety to practice climbing with Rudi in secret.

Franz is Rudi's uncle and one of the most respected Alpine guides in Kurtal. Bound by tradition, he shares his sister's desire to keep Rudi away from mountaineering to protect him. He views the unconquered Citadel as an evil mountain, yet he struggles with his own hidden desire to climb it.

Emil is a physically imposing, highly skilled Alpine guide from Broli. He is a proud man who harbors deep prejudice against climbers from other towns. Saxo operates on the belief that climbing requires only sheer physical power and individual glory.

Ilse is Rudi's mother, widowed fifteen years ago when her husband died on the Citadel. Her lingering grief drives her to forbid Rudi from mountaineering. She hopes to push him into a safe career in the hotel industry, unaware of how deeply he needs the physical and emotional outlet of climbing.

Josef was considered the greatest guide in Kurtal until his death fifteen years ago on the Citadel. He sacrificed his own life and the red shirt off his back to try to keep his injured client warm during a freezing rockslide. His legacy of extreme honor, courage, and selflessness casts a long shadow over the entire village.

An English client who hired Josef Matt and Old Teo to climb the Citadel fifteen years ago. Injured in a massive rockslide on the mountain, he was unable to descend and froze to death alongside Josef, who refused to abandon him.

Klaus is one of the village boys in Kurtal. He frequently mocks Rudi for his small stature, fair skin, and job as a dishwasher, calling him "angel face" and laughing at his lack of ruggedness.

Gretchen is a waitress at the Beau Site Hotel in Kurtal. She has little patience for Rudi's frequent disappearances to go climbing and expects him to complete his assigned chores without excuse.

Hans is a villager in Kurtal who monitors the mountains using a telescope. He provides updates to the local guides about activity on the Citadel, sparking the village's concern when he spots an unauthorized climbing party.