Corpse nightmare 1

In a sweltering room with others. Room is mystical and bilious as if rendered by El Greco. Greasy shadows on the grey walls, etc.
We all lie on mattresses, spaced at regular intervals. They all face north (the direction of winter). There is no wall behind me or to the side of me, giving me a somewhat exposed feeling. The mattress is the old-fashioned horsehair spring type, like you would find in a skip.
I realise with revulsion and horror that beneath the mattress is a corpse. Lying flat like an echo of my own body on the mattress. I am not allowed to move or make sound or the corpse may stir. All of us in the room are under a heavy compulsion not to become agitated lest it should wake the shadowy dead that lie beneath the mattresses.
This image of decay worries me. The corpse had a skeletal face and reminded me of two things. A, the mummified body of a prehistoric hunter that was found in the Alps, about which I watched a documentary a week or two ago. B, a mortuary photo of a murder victim. Face blotched, eyes sunken and skin shockingly white.
We are not allowed to move from the mattresses but I am so uneasy that I leap from the covers and attempt to rush from the room. The others it seems are deep in sleep. A feeling of being pursued by unutterable evil and darkness.
... (I flick on electric light, a bare bulb on the ceiling. There I see quite clearly, from beneath the edge of the mattress, horrible in the harsh light, the sad, skeletal face of the mouldering corpse. "There it is", I say, as though this confirms what I had not really dared to believe.)
I flee downstairs. A horrible feeling of encroachment and pursuit. A feeling of being fundamentally out of place.
Like in my dream of the ruined house.
The house on the ground floor is my gran's old house, a place full of ghosts. I try to find a secluded room, safe from the encroachment of the dead spirits. Desperation and extreme dread, of a type I can't even articulate. The sense of the evil spirits around me is absolutely palpable and very serious.