From publisher blurb:
Within These Walls is a supplement for Asylum that has been kindly written specially for Greywood Publishing by the original author - Pete Lynn.
The Asylum is a horrific place; sparse, lonely, mind-bending and deadly. Enough, in fact, to send anyone spinning into madness. It has been home to the Hofas twins and their various followers for many years, but not all the secrets of the Asylum have been revealed yet and some lie completely undiscovered!
This is NOT a stand-alone product. This supplement adventure requires the QUERP Modern Core Rule Book and the original Asylum adventure to play.