Centurion Adan Longinus strikes out for adventure once again in this third and final book of the Gemstone Trilogy. The family of his adopted brother, Nikolaus, met with traumatic and unexpected deaths, as revealed in Journey of the Pearl. A mysterious device known today as the Antikythera Mechanism weaves itself into the story as the Prophecy Box, which fuels many intrigues and subplots. Adan and Nikolaus, along with Calais, who figured prominently in Quest of the Sapphire, leap from one dangerous situation to another as they gather clues to solve the mysteries of Nikolaus's and Calais's past. When the Prophesy Box is finally found, Adan struggles to control his temptation to use the abilities of the alluring device as he tries to protect Nikolaus from the same temptation. Historical reality fuels the quest for power and dominion by those who have the means to pursue Adan's group, making their path to discovery dangerous and uncertain.