"See, that was easy!" River exclaimed as she balanced precariously on the edge of the precipice, watching with undisguised glee as the salivating half-ton, feral Ravellian wildebeest that had been chasing them plummeted downward into the abyss below.

"Easy!" snorted the Doctor from the mouth of the tunnel a few steps behind her. He shook his head in fond exasperation. She'd only travelled with him a few times so far and already she felt she had the whole universe on a platter. She did, of course, but she wasn't supposed to know it yet. "If that thing had landed on you you'd have been crushed to a pulp!"

River shot him a fierce, swashbuckling grin over her shoulder. "Good thing I ducked, then, isn't it?" she replied cheekily, then swayed as the rocky outcropping on which she stood ominously began to crack.

"River, look out!" the Doctor shouted as the ground beneath her feet – impacted by the tread of the gargantuan wildebeest – started to give way.

She yelped in surprise and threw herself back towards safety, but it was too late – the meter-wide lip of the cliff face on which she was standing crumbled and fell away, carrying her with it.

The Doctor leaped forward at full stretch, crashing painfully into the ground as he caught River's wrist in one hand and thrust the other arm out to snag something – anything – to arrest their fall. His fingers scrambled wildly for purchase as he felt the right side of his body begin to slide over the cliff's rim in River's wake.

A triangular outcropping of rock slammed against his left hand and he clutched it hard, his fingertips molding themselves around it like the sticky pads of a gecko's toes. His body jerked to a halt, his other arm almost pulled out of its socket as his shoulder took all of River's not inconsiderable weight.

He grunted and gasped in a shuddering breath, seeing stars for a moment as pain shot through him but refusing to let go for anything.

They hung there at the very edge of the precipice, suspended by the Doctor's fingertips.

Blinking hard to clear his vision, the Doctor gazed across at the tiny lip of stone that his fingers were grasping for dear life and then down at River, who dangled over inky dark nothingness with only his vise-like grip on her left wrist between her and an endless fall.

This was not good, he thought.

This was very very not good.

"Grab my wrist!" he called, urgency flooding his voice. The abyss stretched beneath them like a bottomless black maw, and if his hold slipped for an instant she would be lost. She had to help him stabilize his grip before he could begin to claw them back to safety.

But her hand didn't move.

"Let me go!" she shouted back, staring up at him with wide, determined eyes. "Save yourself!"

The words stabbed through him like razor-sharp knives. His hearts wrenched with pain and sheer sadness at the thought that, although still so very young, she was already trying to sacrifice her life for his.

After all it was not impossible that he lose her here. Her death, unlike his own, was not a fixed point. Time could be re-written.

But not if he could help it, he vowed silently. And definitely not here. Not now.

Stubbornly he bit his lip and then cranked up his endocrine system, flooding his body with adrenaline and cortisol. Tensing all his muscles he gave a heave borne of utter need and desperation and hauled her bodily upwards, until her outstretched right hand touched the edge of the cliff, gripped, and held on. Panting, he thrust her left arm over the edge and onto solid rock, only releasing his grip on her wrist after she had managed to wriggle her shoulders and chest firmly back onto terra firma.

Only then did he set about pulling himself safely out of harms way.

Groaning with effort, they hauled themselves with scrabbling hands and elbows away from the edge of the overhang, then collapsed side by side at the mouth of the tunnel.

Almost immediately the Doctor scrambled up into a sitting position, his adrenaline still pumping furiously, and drew River into his arms. Cradled her as their bodies shook with exertion. One hand slid into the curls around her ear as his eyes anxiously roamed over her face, scanning it for any sign that she'd been hurt. But her skin, though streaked with dirt, was unblemished and he could sense no pain within her.

Her eyes shone as she gazed back at him, as she reached up with one hand and tenderly caressed his face. "Nice catch, sweetie," she murmured breathlessly, then slipped both arms around his waist and nestled against him, nuzzling his neck with her cheek.

He felt more than heard her exhale a sigh of relief and contentment into his skin and had to swallow down the lump that suddenly formed in his throat.

The Doctor found himself gathering her even tighter to him, squeezing his eyes shut, his hearts still thumping far too hard. He pressed a warm, gentle kiss to her temple.

"I'll always catch you, River." The promise was a soft whisper into her hair. "Always."

FIN