Edison Marshall 
The Splendid Quest [EPUB ebook] 

The lure of recently discovered gold-fields drew them all—Donna and her wise mother; Keith; the lovely Baroness Sonia Sarichef; and later Joe Baxter and an American doctor—to the vast jungles of Indo-China, where safe travel depended on the superstitious fears of strange men speaking a strange language. Mr. Marshall writes a moving story of the mounting passions of two men and two women set against the grandeur and terror of the unknown tropical forests. Surrounded by danger and oppressed by the fear of disease, their finest instincts win in the end—destiny or Kismet, call it what you will, leads them back to happiness.