Handsome Prince Rudolph Krisler's request for help in finding his family's long-lost heirlooms launch Jean and Louise Dana on another exciting mystery while on vacation in Europe. The search for the priceless heirlooms leads from Germany to glorious Switzerland, where the girls and their traveling companions are swept up in adventure and intrigue more dangerous than a thundering avalanche. First, their quest is hampered by a mysterious young man who claims to be a member of the Krisler family. Next, a strange accident nearly costs Louise her life.

Thoroughly mystified but equally determined to unmask their enemies, the girls follow a baffling trail of clues which finally leads them to an abandoned chalet in the Swiss Alps. A trip to the St. Bernard Hospice, a perilous snowslide, a whirlwind escape on skis all play an exciting part in unlocking the dangerous mystery.