Sonja Kurtz - former soldier, supposedly retired mercenary - is in Vietnam carrying out a personal revenge mission when her daughter sends a call for help.
Emma, a student archaeologist on a dig at the edge of Namibia's Etosha National Park, has discovered a body dating back to the country's liberation war of the 1980s. The remains of the airman, identified as Hudson Brand, are a key piece of a puzzle that will reveal the location of modern-day buried treasure - a find people will kill for.
Sonja returns to the country of her birth to find Emma, who has gone missing since her call. It turns out that former CIA agent Hudson Brand is very much alive, and is also drawn back to Namibia. Together, they must finally solve a decades-old mystery whose clues are entombed in an empty corner of the desert.