344 paperback novel. Like new.
While mapping the ancient (now underwater) city of Marinth in the Mediterranean Sea, submersible designer Hannah Bryson discovers the shocking cause of the civilization's doom from a submerged fresco in the city center--the surrounding waters for hundreds of miles were afflicted with what we now call an Oxygen Minimum Zone or a "Shadow Zone", a condition in which oxygen has been leached from the waters, devastating plant and marine life. For an island dependent on such life for their survival, this caused a famine that many did not survive. In Marinth's case, it was caused by a rare algae. Hannah recovers samples of this algae and hands them off to a sister research vessel to take back to land for further analysis, but the samples never reach the lab. The truck en route to the vessel is brutally attacked. Not coincidentally, Kirov finally appears after disappearing for many months and Hannah suspects that the intrigue surrounding her discovery is what brought him back. Soon it becomes clear that someone has nefarious plans to build a master weapon out of this algae and in their desperate race to stop him, Hannah finds herself catapulted into an adventure in which she finds herself even doubting the intentions of her fiercest protector, Kirov.