Sary's Diamonds - Sharon Shipley

Sarabande Swinford has lost her fortune, swindled by an expert con man from whom she gained in return only a handful of worthless paper and a questionable—and partial—treasure map. Taking ship to Cape Town with her lover Tommy and her son Jude, she pursues more of the map as well as its promised treasure, but encounters potential death in many forms.
 
She is separated from her family by plague-fearing mobs, and so goes alone in search of the diamonds the con man suggested the map would give her. Lost, she wanders across Africa’s vast, merciless Great Karroo Desert, accompanied by two men—one a stone-cold killer, the other an enigmatic, charismatic adventurer (but can she trust him?)—and must fight not only for her honor but for her very life.