Mac was no scientist – few people were, these days – but her basic understanding of the Revenant Virus was it caused an extreme electrical reaction in the amygdala, an almond-shaped part of the temporal lobe that controls several emotions, such as anger, love, fear, and sexual desire.

At the same time, the virus destroyed the hypothalamus, that great regulator of emotions such as anger, aggression, and sexual desire. As the hypothalamus failed and the amygdala was super-charged with energy, the victim literally lost the ability to control these emotions.

The first days of the Upheaval had been brutal. Savage, cannibalistic murders claimed the lives of thousands. They were the lucky ones, dying relatively fast. A small percentage of the world population had shown a resistance to the virus – nothing that allowed them to escape the inevitable damage, but which, instead, drove them crazy more slowly. These ones liked to toy with their food, killing and raping with incomparable cruelty and brutality.

The virus had spread outward from a region east of the Cascade Mountains of Washington State that had once been known as the Inland Empire. Loath to bomb their own soil, the American government sought to contain the spread of infection through military-enforced quarantine and the judicious elimination of the infected.

They’d almost succeeded.

What they hadn’t counted on was the long-term effect of the virus on the infected. Over time, the electrical activity calmed, allowing the infected to work together like pack animals. They were not above attacking each other, but because the virus contained two opposing factors – one that healed and one that destroyed, and each was always at war with the other – it was uncommon for such attacks to be fatal.