Robert Neville finds a microscope and learns how to use it. Once he feels confident about preparing slides, he takes blood from a sleeping Undead and studies it. Because viruses are too small to see through this particular microscope, he concludes that the organism he sees is a bacterium; he names it vampiris. Neville experiences “a massive weight of despair” (76) at the discovery, as he barely understands what the discovery means, but eventually grows determined. From his reading, he concludes that vampiris is to blame, not the humans it infects. Vampiris is capable of reproducing spores when their host body does not replenish it with fresh blood; the dust storms caused by military bombings spread the spores.

At the moment, Neville’s only method of distinguishing between infected and true Undead is through shooting them: The infected die to bullets, while Undead are unaffected. He concludes that the infected host vampiris spores, and when they die, vampiris takes over their body, essentially bringing them back to life.

With a better understanding of vampiris, Neville tries to debunk the Undead’s seemingly vampire nature, such as their weakness to garlic. He creates a two-column list comparing Undead traits as explained by science or legend.