Remembering the Origins - a short story

The tunnel wound in labyrinthine twists through the depths of the underwater cavern. A dim light filtered through its membranous walls, blood red and eerie. The two children, their hands grasped together crept forward past smaller caves and other passages, constantly aware of the danger lurking within the depths of the only world they knew.
This was how it was. Always seeking refuge, always on their guard, tiptoeing forward, voices hushed - when they dared to speak at all.
The girl was the stronger of the two, more courageous. The boy was timid – not weak but of a more delicate nature – not created for a world such as this. He looked to his twin for guidance. She in turn focused on protecting them both.
She stopped and he felt the tension running from her arm into his. He paled, trembling. She squeezed his hand and pulled him into a nearby cave. They waited, listening, barely breathing.
In the distance they could hear the sound of damp slithering. They felt the presence of the creature seeking them, its tongue flickering, its maddened red eyes glancing this way and that. They could feel the movement of its search vibrating through the venous walls of the cavern, that living cavern that pulsated and throbbed in its self-created glowing light. It was a place that should have sustained and it was a light that should have nurtured them. Instead it was a place in which they were hunted, forced to live on their wits, terrorised at every twist and turn.
“It’s coming closer,” said the girl. “We must get out of here. It will sniff us out.”
“I’m frightened,” said the boy.
“I know, but we must get out of here before it gets any closer.”
The risk was great, they both knew it.
The boy quailed at the thought. He didn’t know how much longer he could go on like this. This was not a world in which he wanted to live. And if it was a taste of the world beyond, the world to which they were destined to go, then…
His knees buckled beneath him.
“I can’t go on,” he said looking up at his sister, his eyes weary, pleading.
“You must,” she said, tugging at his hand, pulling him to his feet.
“I can’t. I’ll slow you up.”
“No, you won’t, I’ll help you. I’m not leaving you here.”
He pulled his hand from hers as the serpent’s hissing breath slunk closer.
“I can’t do this anymore. I can’t. I haven’t the strength for this. Not anymore. I can’t go on.”
“You must,” the girl insisted. “I can’t leave you here.”
“No,” the boy said, gazing into her face, his expression softening. “This is no longer my journey. You have to go on alone.”
“But I don’t want to,” she whispered, struggling not to let her voice break into a wail.
He smiled at her. “I don’t think there’s a choice.”
She stared at him, at his pale, beautiful face. He may have been the frailer one, but the serenity of his wisdom was something she couldn’t doubt. He wasn’t meant for this world, nor the one beyond. His journey ended here. She knew that. Just as she knew it was only her resilience and fortitude which would enable her to survive - her sheer bloody-mindedness.
“Are you sure?” she said.
He nodded.
Her heart breaking, she turned from him and slipped across the passage, ducking down a side tunnel. Turning back for a brief moment, she saw the red and black of the serpent’s scaly body as it undulated in sinuous motion, its eyes glinting with self-obsessed greed, towards her brother.
Now she was on her own. And she would outwit it at every turn. It had got one of them, it would not get the other. She would fight it to the bitter end, she would fight for both of them, in this world, and in the sunlit one beyond.