Whom the gods would destroy they first make mad...

Humans and mers have reinstated an alliance long abandoned, and the sea demons no longer threaten the Bahamas. The underwater civilizations are at peace for the first time in millennia.

Then a devastating plague returns to devastate the submerged cities, turning mers into insane, ravening beasts. A plague that invariably ends in death.

Legend says a cure lies hidden somewhere in a secret cave, and newlyweds David and Faryn set off with their friends to find it. Only then is the true source of the disease revealed—an evil being as old as time whose hatred of the mers will only be satisfied when their entire civilization has been destroyed.