The mysterious sinking of three freighters sends Nancy out West to search for those responsible. Suddenly, she is kidnapped and placed aboard an airplane. She finds herself in the company of a young and frightened stowaway, Elena, on her way to visit an aunt in South America. When they arrive at their destination, Nancy finds that she is not the only prisoner — Elena’s aunt is being held also!
Determined to rescue the elderly woman and free herself as well, Nancy works out an ingenious plan with the help of Elena and her fiancé. In the process, she discovers hidden treasure that may well be the missing link in this bizarre and dangerous string of incidents.