Teeth clamped around the regulator, he breathed again. The stubborn drag told him the pony was nearly spent. He almost lost it when a violent surge sent him spinning sideways. For a moment, his legs were extended, and he snatched them back in as the wall of the passage grazed his foot.

He knew the passage had widened into a great chamber, for his speed and rate of spin decreased. Nash tentatively opened his eyes to a black nothing. His head torch was gone. So, too, his mask. Tumbling slowly end over end, he felt like an astronaut, untethered from his spaceship, drifting deeper into space. Somehow the Beatles’ ‘Tomorrow Never Knows’ began playing on some synaptic sitar. Oxygen toxicity? In the icy water, he could only surrender to the void like an embryo floating in a vast stone womb.

He began to accelerate again, and a sudden series of S-bends flung him all out of shape. Legs akimbo, desperately clutching the cylinder, he sucked in a last puff of air and the pony was dead. Releasing it, he heard a savage clank as it impacted the invisible rocks hurtling past. The incredible speed was unrelenting, a limestone sleigh ride from Hell which went on and on . . .

He was becoming hypoxic. Lungs burning, his diaphragm went into involuntary contractions as the carbon dioxide build-up demanded autonomic respiration. His whole body, every last cell, was ablaze . . .

And then, suddenly, the pain vanished. Was replaced by pure elation. And, in its thrall, Natalie came to share the penultimate moment with him. His Natalie, with that mysterious smile, her peach-curve chin, her beautiful smell of frangipani and coconut cream. He felt her soft hands stroking his face, and in that loving embrace, he understood she now forgave him everything, and he was so joyful, because now at last he could surrender. Now he could let go and just breathe . . .

‘Robert . . . Robert . . . Robert!’

He froze, as she shook him violently.

Nash blinked in surprise. Natalie was demanding that he live. She was turning away, ascending into the light, and all he could do was follow . . .

Where once he had erupted from the Sepik like a creature spawned in Hell, this time he was reborn. Risen to the surface of the Hoosenbeck in a boil of green-white water.

Oh God, how that first breath hurt. Exquisite agony. And then, the deep sucking gasps, the sounds of air, of white water, of rain and birds calling.

Nash slowly side-crabbed towards the bank. Weak and exhausted, he grasped hold of some reeds and pulled himself out. It took him a moment to recognise where he was, for the water levels had changed so dramatically. It was the resurgence pool, two kilometres downstream of the sinkhole.

And then he remembered Mia.

Tearing off his drysuit, he began to run.

Chapter 40

Chapter 40