Kamzin has always dreamed of becoming one of the Emperor's royal explorers, the elite climbers tasked with mapping the wintry, mountainous Empire and spying on its enemies. She knows she could be the best in the world, if only someone would give her a chance.

Kamzin dreamed of becoming one of the Emperor's royal explorers, the elite climbers tasked with mapping the wintry, mountainous Empire and spying on its enemies. Then River Shara, the greatest explorer ever known, arrives and demands to hire Kamzin-- not her older sister Lusha, as everyone had expected-- for his next expedition. River's mission to retrieve a rare talisman for the emperor; it means climbing Raksha, the tallest and deadliest mountain in the Aryas. When Lusha sets off on her own mission to Raksha with a rival explorer, Kamzin must decide what's most important to her: protecting her sister from the countless perils of the climb or beating her to the summit.