In the bitter chill of winter, over snow-covered mountains and against all odds, one fearless young girl will risk everything to guide her friends to safety. Fifteen-year-old Heidi (Caton) leaves her beloved grandfather (Jan Rubes), her childhood sweetheart (Sheen) and her cherished Swiss mountains to attend an Italian boarding school run by a kind headmistress (Caron). But when World War I breaks out, Heidi and her classmates are torn from their serene surroundings. Fearing for their lives, they escape on foot through the countryside...and embark on a daring trek across the treacherous, frozen Alps towards the safety of Heidi's girlhood home.