The book is in four sections:
- "The Shadow of Mount Elgon" delves into the history of filoviruses, as well as speculation about the origins of AIDS. Preston recounts the story of "Charles Monet" (a pseudonym), who might have caught Marburg virus from visiting Kitum Cave on Mount Elgon in Kenya. The author describes the progression of the disease, from the initial headache and backache, to the final stage in which Monet's internal organs fail and he hemorrhages extensively in a waiting room in a Nairobi hospital. This part also introduces a promising young physician who became infected with Marburg virus while treating Monet. Nancy Jaax's story is told. Viruses, biosafety levels and procedures were described. The Ebola virus disease outbreaks caused by Ebola virus and its cousin, Sudan virus, are mentioned. Preston talks to the man who named the Ebola virus.
- "The Monkey House" chronicles the discovery of Reston virus among imported monkeys in Reston, Virginia, and the following actions taken by the U.S. Army and Centers for Disease Control. It starts with the monkey house receiving a shipment of 100 wild monkeys. After four weeks, 29 of these monkeys have died. This is followed by the veterinarian for the facility, Dan Dalgard, examining the dead monkeys and sending the samples to Peter Jahrling, a virologist at United States Army Medical Research Institute of Infectious Diseases. After seeing a rope-like virus under the microscope, it is suspected that the monkeys were infected with a hot agent similar to the Marburg virus. Jahrling then conducts a blood test to find out that the hot agent is the Ebola Zaire virus. This conclusion leads to the Army Medical Research Institute deciding to euthanize all the monkeys in the same room as the infected monkeys.
- "Smashdown" is more on the Reston epizootic, which involved a strain of the virus that does not affect humans but which easily spreads by air, and is very similar to its cousin the Ebola virus.
- "Kitum Cave" tells of the author's visit to the cave that is the suspected home of the natural host animal in which Ebola lives.
The book starts with "Charles Monet" visiting Kitum Cave during a camping trip to Mount Elgon in Central Africa. Not long after, he begins to suffer from a number of symptoms, including vomiting, diarrhea and red eye. He is taken to Nairobi Hospital for treatment, but his condition deteriorates further, and he goes into a coma while in the waiting room. This particular filovirus is called Marburg virus.
Dr. Nancy Jaax had been promoted to work in the Level 4 Biosafety containment area at the United States Army Medical Research Institute of Infectious Diseases, and is assigned to research Ebola virus. While preparing food for her family at home, she cuts her right hand. Later, while working on a dead monkey infected with Ebola virus, one of the gloves on the hand with the open wound tears, and she is almost exposed to contaminated blood, but does not get infected. Nurse Mayinga is also infected by a nun and goes to Ngaleima Hospital in Kinshasa for treatment, where she succumbs to the disease.
In Reston, Virginia, less than fifteen miles (24 km) away from Washington, D.C., a company called Hazelton Research once operated a quarantine center for monkeys that were destined for laboratories. In October 1989, when an unusually high number of their monkeys began to die, their veterinarian decided to send some samples to Fort Detrick (USAMRIID) for study. Early during the testing process in biosafety level 3, when one of the flasks appeared to be contaminated with harmless pseudomonas bacterium, two USAMRIID scientists exposed themselves to the virus by wafting the flask. The virus found at the facility was a mutated form of the original Ebola virus and was initially mistaken for simian hemorrhagic fever virus. They later determine that, while the virus is lethal to monkeys, humans can be infected with it without any health effects at all. This virus is now known as Reston virus.
Finally, the author goes to Africa to explore Kitum Cave. On the way, he discusses the role of AIDS in the present, as the Kinshasa Highway that he travels on was sometimes called the "AIDS Highway" after its early appearance in the region. Equipped with a hazmat suit, he enters the cave and finds a large number of animals, one of which might be the virus carrier. At the conclusion of the book, he travels to the quarantine facility in Reston. He finds the building abandoned and deteriorating. He concludes the book by claiming that Ebola will be back.
