I'm afraid I can't be very specific at all with this, as I'm describing a memory of someone else's description of a short story that they had themselves read, but I'm absolutely convinced this is an existing story. Here is what I remember:
- I believe there is a group of astronauts that arrive on the Moon, Venus, Mars, or some other alien world.
- The world is either uninhabited or inhabited by hospitable aliens that welcome the astronauts into their society; I'm convinced it's one of these two
- Soon after some short exploration, one of the astronauts "wakes up" to find himself back on the ship (I think) and a formless being, like a cloud of fog (or something more overtly malicious, but I'm pretty sure it's non-corporeal) standing over him
- The story either ends there, or with him going (back?) to sleep
Regardless of the other details, and I apologize I can't be more specific with them, the overarching implication was that this astronaut's experiences have been somehow manipulated by an alien being he has encountered on this strange world. It's possible he looked over to see his fellow travelers in the same position as he, with aliens poised over them as well.
Do these vague details bring anything to anyone's mind? I'm determined to find the original story (which I'm sure exists) or at the very least something like it.