#1 international bestselling author Andrew Pyper, critically acclaimed for his novel Lost Girls, returns with a gripping story of raw courage, crippling fear, and the overwhelming human instinct for survival. At the dawn of the new millennium, twenty-something dot-com millionaires Wallace and Bates travel to Brazil to market their breakthrough product, Hypothesys -- a "morality machine" designed to help people make the best decisions of their lives. But when they impulsively join an eco-tour deep into the Amazon rain forest, they may have sealed their own dire fates....In the dead of night, their boat is attacked, and Wallace and Bates are kidnapped along with their enigmatic female interpreter. Imprisoned and savagely tortured, they struggle to hold on to their humanity. But after Wallace engineers a violent escape, the survivors' own hidden dark natures begin to emerge -- posing a threat more lethal than either the jungle that surrounds them, or the merciless gunmen who pursue them.