My review -
John Marshall is sent to the abandoned facility at Orford Ness to repurpose it for radio broadcasting. It was the centre of a secret project known as Cobra Mist. When he enters the buildings he becomes subject to what he thinks are migraines. Another worker there had reprogrammed Cobra Mist to run a secret project of his own.
This is a study of personal reality. Who are we? How do we know? Who is dreaming and who is the dream? There is a Matrix-like quality of wondering what truly exists. I found this story very creepy, partly from the feeling it so brilliantly conjures that the mind is fragile and its contents may not be real. Partly, too, it was my own phobia of abandoned building which ramped up this feeling of unease throughout the story. A very good read for lovers of sci-fi and speculative fiction.