John Buchan 
The Courts of the Morning [EPUB ebook] 

South America is the setting for this adventure from the author of ‘The Thirty-nine Steps’. When Archie and Janet Roylance decide to travel to the Gran Seco to see its copper mines they find themselves caught up in dreadful danger; rebels have seized the city. Janet is taken hostage in the middle of the night and it is up to the dashing Don Luis de Marzaniga to aid her rescue.