Short novel (1961-1965.) On a space station at the outskirts of our solar system works a fat man who is controlling the returning pilot who was exploring some distant galaxy.
The pilot is in deep sleep with tied hands and legs on a bed in a big room whose ceiling can be opened to open space which will destroy everything in that room.
The fat man can penetrate into the pilot's dream and see what the pilot sees in his dreams.
That is the special ability of that fat man who is sitting beside the bed with the tied pilot.
In the dream the pilot is diving deep in some sea entering a big pyramid on the bottom, going through the labyrinth in the pyramid until he finds himself in some central room in the bottom of the pyramid with some flat vertical surface covered with a curtain.
He pulls aside a curtain and that is a mirror with the face of the fat dream-spy.
He finds himself tied on the bed and saw his own fat body quickly leaving the big room and heard his own voice: "Quickly, open the ceiling, it's an intruder!"