One hundred miles off the coast of Puerto Rico, a top secret experiment too dangerous to be conducted on land is being conducted aboard the U.S. nuclear attack submarine Sam Houston—an experiment that has gone horribly wrong.A predator is loose in the Sam Houston—a microscopic killer that strikes without warning, driving its victims to terrifying heights of violent, self-destructive insanity.Soon madness and terror reign eight hundred feet below the ocean's surface, as those infected race to defeat the silent killer—unaware that another enemy follows in their wake. A diesel submarine relic is pursuing nuclear-powered Sam Houston into a final, deadly confrontation in the deepest waters of the Atlantic.