Climber A remained at base camp. Climbers B, C, D & E carried on to the summit. Climbers C,D & E returned a few days later to base camp and told Climber A that Climber B died in an avalanche. Later that night, climber B returned and told Climber A that it was C,D & E who died and A has been talking to ghosts. Who is telling the truth?
"Who to Believe" (相信誰)
According to this site, Bleeding Mountain (possibly the same film as Demon in the Mountain is based on this short story:
Bleeding Mountain is adapted from a short online ghost story, Who to Believe <相信誰>. This popular 140 word short story has been circulating for a long time and it is finally adapted into a thrilling horror movie.
It seems to fit the plot, too:
Surprisingly, in the middle of the night, Ron covered in blood appears in front of her. Ron reveals that during the first day, there was an avalanche, and everyone was killed except for him. Who should Stephy believe? Are the mountain climbers humans or ghosts? Most importantly, is Ron now dead or alive?
From what appears to be a version of the story, machine-translated:
Then her boyfriend tells her: the first day of the attack took place on the mountain peak hard! All the other people are dead and only he is still alive. Do you know who to believe?