It all begins in 1865. Somewhere beneath Pennsylvania, in darkness. A distant sound is heard. A whirring... Suddenly, the wall explodes and a gigantic drill bit bursts through, revealing a train-like cab and locomotive wheels encased by sharp, metal treads. This metal beast is known, simply, as THE MONOLITH. Explorers emerging from the cab look at the massive cavern they are standing in, and declare that they have found it - The Hollow Earth. From the darkness, something slithers up the cab, kills the lights, and the explorers are never seen alive again... A century later. 1983. It's a rainy day in Eastern Pennsylvania. Two friends, Mike and Brian, are bored at Brian's house. While down in the basement, they uncover the key to Brian's grandfather's house - abandoned since the mid-60s and presumed haunted after his grandfather mysteriously disappeared.