pBusiness had originally brought the Hollister family to Europe. Then a new and exciting mystery led Pete, Pam, Holly, Ricky, Sue, and Mrs. Hollister on a thrilling chase while Mr. Hollister returned to America.ppHigh in the Swiss Alps, a suspicious stranger in a cable car dropped a large black key which the Hollisters found. An insurance investigator named Johann Meyer was following the stranger, an international jewel thief. Mr. Meyer told the Hollisters about his dangerous case--to find a large diamond that had been stolen from Holland. When Mr. Meyer's small plane was reported missing over the mountains, the Hollisters decided to help.ppThe trail took them to a small village high in the mountains where Holly thought she saw the stranger again. But the man escaped before they could catch him. Then Pete and Pam discovered a ruined chalet which yielded another clue--a round metal disc that they later identified as a diamond saw. But who, they wondered, was blowing the long Alpine horn