An unprecedented medical mystery: how did U.S. President Paul Ralston become infected with the HIV that developed into AIDS? And what, if anything, should the American public be told? National security and political stability are at stake.

Dr. Martin Riker, an expert retired from CDC and the Army, is urgently summoned to the White House to track down the source of the HIV. His main possibilities: enemy plot, medical accident, extramarital sex, and IV drugs.

He discovers startling intimate behaviors, and accesses confidential government and public health information. To locate sexual contacts, he reluctantly finds ways to obtain names and addresses despite rules supposedly protecting the privacy of patient information. Blood tests and viral DNA analyses help exclude some suspects. Some unusual angles take him beyond the bars of Washington, to Maine and Tokyo.

As the list of possible sources shortens, he is confronted with false evidence being planted, a murder, and a suicide. Finally, Riker pieces together the astounding situation which led to the Commander-in-Chief's infection.

The book ends when President Ralston decides whether the country should be informed of his disease and its source.