When Jeremy Ross, a twenty-four-year-old medical student, agrees to help a former girlfriend investigate her father's death, he has no hint of the gauntlet that lies ahead. Soon he's confronting both a powerful conspiracy and the recurrence of a serious medical condition that threatens his self-control.

Determined to press on, he follows up on his only lead - a colossal research center in South Carolina called Tucsome. Once inside the facility, he makes two startling discoveries: Tucsome receives billions more in government funding than anyone imagines, and its brilliant chief scientist has somehow found a way to crack the genetic code. Amid more revelations and deaths, Ross begins to understand the horrifying implications of what will happen in seventy-two hours. Unless he can stop it.

Before he is through, Ross will go up against the government's most elite agents, nature's most formidable obstacles, and science's most daunting mysteries - all with the aid of only one person, the beautiful woman who has reentered his life. At each turn, he will be called on to think his way out of calamity, to draw on the resources of his prodigious mind. And invariably, the solution will emerge.

What he doesn't bargain for are the personal demons that rise up and threaten him at the end, presenting him with his greatest - and perhaps insurmountable - challenge.