Ben Gold sacrificed his ship in an effort to prevent pirates from attacking the hidden city of Tamoanchan. Now Malik, an old friend turned enemy, has captured Ben and Miranda—the scientist Ben loves. With Miranda held hostage, Ben has to do Malik's dirty work.

Miranda has plans of her own, though. She has developed a test for the virus that turned most of the population into little more than beasts called Ferals two generations ago. She needs Ben's help to rescue a group of her colleagues to perfect the test—but first they must rescue themselves.

When a terrible new disease starts spreading across Tamoanchan and people start dying, it seems there's something more sinister afoot. Then an old enemy attacks. Can Ben fight off the invaders? And will it be in time to save anyone from the disease?