"Ah, the glow of a dying world," the Doctor exhaled, leaning out of the Tardis door as she drifted through the void. He was riveted by the strange marriage of despair and beauty taking place in front of him. Half-a-dozen light-years away, a world was burning.

"Is it meant to be purple?" River asked, perched on the floor with her legs dangling out into nothingness. She was flicking through a thick book, trying to find the world's name from a directory of stars and their assorted worlds. "It never ceases to amaze me that for all the wonder of the Time Lord empire – you still favour books."

"Books are cool..." his face fell in a pout. He was wearing that damn fez again, the red hat slipping dangerously close to falling off his head.

"Books are heavy," River easily countered, as she checked the star's position. It was a blue giant, boiling a long way from the exploding planet. Even so, its immense mass and gravity tides were ripping the poor planet to pieces. Infanticide – of sorts. Galactic murder.

"Honestly River," he gripped the door in defeat, "I bring you to one of the most beautiful sights in the universe and you're down there – reading."

"I already said it was pretty."

"Pretty? Beautiful – stunning – pulchritudinous – ravishing."

River looked up from her book with a disapproving expression.

"Okay – maybe not ravishing."

"Better not be." River found what she was looking for, her scarlet nail tracing a line of text. "Unknown World, K29-W system. Only satellite of blue giant star. Planet death -" she checked her watch, "-today." River pointed at the scene in front of them, another gasp of dying world shedding out into the darkness. "Star death, one billion years from now." She snapped the book closed and looked up expectantly at the Doctor.

"You've got that look..." he said suspiciously.

River tilted her head slightly, blonde curls bouncing. "What look?"

"The, 'can we do something very unwise and most likely dangerous' look."

The Doctor shifted his gaze between River and the burning purple mass behind. There was something about that world that stuck in his throat. It was unfinished. All things come to an end but not without running their proper course. He could feel it too, Time was calling out to the Tardis and to him. His Tardis didn't picks worlds at random, she always took him to where he needed to be; the epilogue or prologue of other people's stories.

"Fine," he finally agreed. "But we're not stopping at the gift shop this time. Swear it..."

River raised her hands in surrender. "No shopping, I promise."

It was remarkably easy for River to keep her promise. The planet was barren.

"Oh my..." River breathed, gazing up at the black carpet above the world, littered with stars. "It's like being on Earth's Moon."

The Doctor, dressed in his usual tailored suit pants, white shirt, red suspenders and matching bow tie; hadn't bothered with a jacket. The air was dry and warm. Several inches of sand crunched underfoot and beneath that, fresh volcanic rock. The world was young and old – reformed and gnarled by layers of violence. A half-hearted sweep of mountains loomed off to the side and in front of them was nothing save the gentle arc of the horizon.

"There's a forcefield keeping a thin layer of atmosphere in place. Transparent – see? Not enough atoms in the sky for the sun's light to bounce off and create pretty coloured sky. It's just – black."

"I quite like it," River strolled with her head still tilted upwards. "It's alien."

"Everything is 'alien' to you, my dear," he pointed out. She swatted him sharply. "Sorry."

"Take off that damn hat – you look like a pet monkey."

The Doctor reached up, protectively stroking his hat. "No. The Fez is cool."

'Cool' was his word of the month and if he said it one more time, River was going to handcuff him to something disagreeable. And there he went, wandering off into the desert.

"Doctor?" River followed, crouching down beside the Doctor. He was staring intensely at a trail of footprints heading off in the direction of the mountains. "I thought this world was abandoned?"

"No," the Doctor brushed his hand through the sand. It was warm, heat radiating out of the ground. The warmth certainly wasn't coming from the distant blue star. It was coming from below, from the liquid core of the planet spinning in fiery vortices. "The Tardis detected a single life form."

"A person?"

"I don't know. It was more of a ghost – an impression spread over the world. I'm not even sure if it's sentient. Life is a broad definition." He placed both palms to the sand. "There's two hundred years until this world breaks apart but you can already feel it shaking."

A grin spread over River's lips. "You think you can save it – and here I was thinking we'd stopped for a bit of idle sight-seeing."

"There's nothing in the laws of the universe to prevent us from doing both." He straightened up and gazed over to the mountains. "Let's idly sight-see in this general direction..."

Though unimpressive from the plains, the gentle mountains proved onerous. What they lacked in height was overcompensated with slopes of chalk-like sand, sheer cliffs and burning cracks in the earth where fire bubbled to the surface. The footprints continued and the Doctor followed them, eventually dropping to his hands and knees to claw up the final dune.

River and the Doctor were made filthy by the dirt. It was grey, sometimes bordering on violet and so fine that it stuck to everything. They coughed out the residue in their lungs, eyes watering with purple tears.

"I think I'm done sight-seeing now..." River coughed from behind, momentarily vanishing in a puff of dirt as she slipped a few feet backwards. The angle of the slope was deceptive. When the Doctor looked back over his shoulder, River was perfectly silhouetted against the black sky with no sign of the sweeping plains below.

"Adventure is what we do," the Doctor insisted, that irritating grin on his face. His Fez was annoyingly untainted, still perched on his brown mop of hair. "Remember the Six Cities of Carnivorous Fruit Trees? Whole planet of tiny ant-people worshipping plants accidentally dropped by a space ship – remarkable!"

River was about to reply with a quip about there being more meritorious things to explore when she saw a small, emaciated boy sitting cross-legged, staring out over the lands below. "Doctor..." she murmured, nodding at the child.

"Ah, our mysterious life form, I presume."