Plot Summary and Character Descriptions

Main Characters

Dr. Jeremy Stone - Professor of Bacteriology at the University of California at Berkeley; a Nobel Prize winner.
Dr. Charles Burton - Professor of pathology at the Baylor College of Medicine
Dr. Peter Leavitt - Clinical microbiologist; suffers from epilepsy
Dr. Mark Hall - Medical doctor and surgeon.  Hall is the "Odd Man" and he is given the key that can disarm the nuclear bomb that would wipeout the laboratory in the case of a contamination. 

Plot Summary

1. A military space capsule lands in Piedmont, Arizona.  Radio connection with the capsule is lost, and a team sent to go recover the satellite find every member of the town it landed in dead, except for two people--an old man and an infant.  The survivors and the satellite are taken to an underground laboratory to be studied by the Wildfire team (a government sponsored team of scientists that counters extraterrestrial biological infestation).
2. The scientists believe the satellite returned with a deadly microorganism that kills by nearly instantaneous lethal blood clotting. Upon investigating the town, the Wildfire team discovers that the residents either died in mid-stride or went insane and committed bizarre suicides. Two Piedmont inhabitants, the sick, Sterno-addicted, Peter Jackson; and the constantly bawling infant, Jamie Ritter, are biologic opposites who somehow survived the organism.
3. Further investigation determines that the bizarre deaths were caused by a crystal-structured, extraterrestrial microbe on a meteor that crashed into the satellite, knocking it from orbit. The microbe contains chemical elements required for terrestrial life and appears to have a crystalline structure, but lacks DNA, RNA, proteins, and amino acids, yet it directly transforms matter to energy and vice versa. 
4. The microbe is code named "Andromeda". It mutates with each growth cycle, changing its biologic properties. The scientists learn that Andromeda grows only within a narrow pH range; in a too-acid or too-basic growth medium, it will not multiply — Andromeda's pH range is 7.39–7.43, like that of human blood. That is why the old man and the screaming baby survived: both had abnormal blood pH. However, by the time the scientists realize that, Andromeda's current mutation degrades the plastic shield and escapes its containment. Trapped in an Andromeda-contaminated laboratory, Dr. Burton believes he is on the verge of death. Burton survives because Andromeda has already mutated to nonlethal form.
5. The self-destruct atomic bomb is automatically armed when it detects a containment breach, triggering its detonation countdown to incinerate all exo-biological diseases. As the bomb arms, the scientists realize that given Andromeda's ability to generate matter directly from energy, the organism would feed, reproduce, and ultimately benefit from anatomic explosion.
6. To halt the atomic detonation, Hall must insert his special key to an emergency substation anywhere in Wildfire. Unfortunately, he is trapped in a section with no substation. He must navigate Wildfire's obstacle course of automatic defenses to reach a working substation on an upper level. He barely disarms the bomb in time before all the air is evacuated from the deepest level of the Wildfire complex. Andromeda eventually mutates to a benign form and is suspected to have migrated to the upper atmosphere, where the oxygen content is lower, better suiting Andromeda's growth.