That sure is a cave mouth that isn't on his map. It must have been recently exposed by a very small landslide, judging from the exposed dirt. The weather's been dry now for weeks, and vigorous thumping doesn't make the ground collapse further. Walking into it is not the safest thing he's ever done, nor the most dangerous.
There's a sound, in the cave. It sounds like radio static, and like a woman's voice quietly crying in the distance, distorted by echoes. It sounds like a chorus of whispers and wind blowing through leaves and small creatures with many legs skittering over stone. It sounds like all of these things and none of these things and any of these things, simultaneously and by turns.
It's coming from just slightly farther in than he can see from the entrance.
That's odd. What is that?
Perhaps somebody got here first and is having a very spooky party. Perhaps he should just leave them be.
But what is that sound?
He heads deeper in, flashlight and walking stick in hand.
First there's a slight curve to the right, taking him out of sight of the entrance, so that its light is only visible behind him where it shines on the dirt and rock.
Then, a little deeper in, there's a shadow.
At first glance it looks like the beam of his flashlight has silhouetted a woman against the cave wall, a woman with long hair and a ragged dress. But the arms are unnaturally long, and skeletally thin, with gaps in places where even a skeleton would not have gaps. And within the shadow of her torso are deeper shadows, curved like ribs, revealed and concealed and revealed again as her body seems to swirl like mist around them.
She makes the sound again. It rises and falls like speech, but there are no words or even really phonemes discernible within it.
He does not drop his flashlight, but if it were not sturdily built, it might creak in his grip, and he jumps back a bit and just barely saves himself from a fall on the irregular floor.
In the unsteady beam of the flashlight, her head (or its shadow?) slowly tilts to one side.
She makes another sound, a burst of static/a rasping croak/a low whistle like air over the mouth of an empty bottle.