Moments later, he had awoken with a start, and sat up convulsively. His body worked again. He threw off the heavy duvet and swung his feet off the bed, turning to face the dying fire a few feet away. No one else was in the chamber. The massive fortress-style door was still bolted. The nightmare impression, which had been so convincing a minute ago, now seemed ridiculous. Lying back down experimentally, he looked up and saw that the lamp on his bedside table was casting a firelight shadow onto the canopy above him, and that the shadow moved about as the fire flickered and the logs settled. He must have half-opened his eyes while sleeping and interpreted this as the shadow of a man.

So the nightmare had an explanation. Still mysterious, though, was the absolute paralysis that had trapped him in that bad dream. Later, Richard had learned that this was a well-recognized and scientifically verified phenomenon known as sleep paralysis. Primitive cultures identified it as some form of enchantment, or made up stories about eldritch night-stalking creatures that would sit on your chest and pin you to your bed and suck the air from your lungs and the screams from your throat.

But there was a perfectly reasonable explanation for it. When you were awake, your brain could of course control your body. When you slept, however, you tended to dream. And in your dreams you could run, fight, and talk. But if the body continued to answer commands from the brain, you’d be thrashing all over the bed, vocalizing, and so on. So a mechanism had evolved whereby, at the moment that the thread of consciousness was severed, the link between brain and body was cut, like throwing a switch. And at the moment you woke up, the switch was thrown back to the “on” position and you went back to moving around as you always did. Normally the system worked with an amazing degree of perfection, so most people lived their whole lives not even knowing that it existed. But every system had glitches. The jolt you sometimes made while drifting off to sleep was one such—it happened when the switch was a fraction of a second late going off. Another, much more impressive and terrifying sort of glitch happened every so often, especially to people who—as in Richard’s case on the Isle of Man—were sleeping off of their accustomed schedule. You would wake up, but the switch would not be thrown to “on” and so you would remain as perfectly paralyzed as you had been a moment ago while sound asleep. Just like a person who, while seeming to slumber and breathe peacefully, is in fact having a terrible nightmare, you would lie there with eyes open in perfect, inescapable repose, unable to do anything about the imaginary monster on your chest, the intruder next to your bed, the fire consuming your house.