More than large furry spiders or the famous, but rarely-spotted, Boogy man, what really frightens us about the dark is that we are in a world where nothing exists outside ourselves. Only the sound of our own breathing. The thump, thump of our heart. And after a few minutes of silence, the low whistling of the blood flowing in our ears. The sound of nothing.
Darkness is the absence, the withholding, of the world outside.
Ostensibly, this was a very benign plague. No blood turned to water. No-one suffered excruciating boils. A darkness that at first prevented you from seeing someone even if they were right in front of your face, and then it became even thicker until it literally froze people. The answer is that, in the dark, I perceive that there is nowhere outside of me.