Disclaimer: I don't own any part of Doctor Who, unfortunately.
River stood back watching the Doctor run around the TARDIS console, flipping switches and pressing buttons. He seemed especially pleased with himself and she did so enjoy when he was like that.
The Doctor called from the other side of the platform, "I do like seeing that look on you."
She snapped out of her thoughts. "What look?"
He came around the console again, grinning at her. "You know, that look you get when you think I'm being particularly clever."
"You always think I'm thinking that!" River was thankful he had his back to her as he made another circuit around the platform so he didn't notice her eyes confirming his suspicions.
"I'm always right, too." He came from behind the console carrying a cloth-covered basket and asked, "So! Niagara Falls! You know it?"
"Of course, but that's a little mundane for you, isn't it?"
The Doctor took River's hand and led her down the steps as he replied, "Yes, and that is exactly why we're not going there!" He paused by the doors and lightly tapped the tip of her nose. "Imagine Niagara Falls; only it flows upward. And it isn't actually water. More like… liquid light. So really nothing at all like Niagara Falls, then, but there you are."
As he pushed open the TARDIS doors, the most amazing sight awaited them. A ribbon of light, rather like the aurora borealis on Earth only more solid, stretched out as far as the eye could see. The curtain had the brilliance of innumerable prisms and nearly the appearance of billowing silk. It had to be more than just light. River had never seen light like that and she'd been on planets with every different color of star shining through every type of atmosphere imaginable. She noticed the hairs on the back of her neck stood up but wasn't sure if it was from the majesty of the scene or the slight charge in the air.
"Doctor Song, you're speechless."
"I'm never speechless," said River, matter-of-factly. "I just don't have anything to say at the moment."
"I do believe that's the definition of speechless." He grinned and bowed to her, holding out his hand. "Milady?"
River hesitated. Light had to mean heat, or electricity, or something. Just because something was beautiful doesn't mean it wouldn't kill you. No one knew that better than her.
Still in a bow, the Doctor tilted his head to look up at her. "Come now, don't you trust me?"
"You know the answer to that, my love." River took his hand and followed him toward the curtain of light.
The Doctor entered first, his hand still laced with hers. A slight shudder transferred from him to her through his fingertips. She only had a moment to wonder about its cause before the curtain engulfed her.
Traces of electricity ran though River's body though it didn't hurt; quite the opposite, actually. A delicate tingling sensation covered her skin like statically charged silk on a dry winter day. Warm and cool at the same time, it felt as if she had been kissed over every inch of her body all at once. She felt her knees weaken and the world began to tilt. Or perhaps she was falling. It didn't really seem to matter very much. The next thing River knew, she was wrapped in soft warmth that smelled of all her favorite things. She raised her head to see the Doctor smiling down at her and realized he was completely supporting her. As she regained her footing, she opened her mouth to say something but found there were absolutely no words in her mind.
"Now I know you're speechless," he said as he brushed some stray curls from her face.
"Now I'll admit you're right," she whispered breathlessly.
The Doctor took a step backwards, holding his arms out and gesturing at the cavern they had entered. Banners of impossibly thin crystal curved their way along the ceiling, twisting and turning like a carnival maze. The walls were of a rougher stone but were inset with minerals that refracted the light brilliantly around the area.
He watched her take it all in, just as entranced with her as she was with the cavern. The way the light reflected off her eyes, the highlights of her hair, and the shimmering silk of her dress – it made her look magical. He longed to touch the vibrant cloth snug against her curves, to let his fingers dance among those wild curls. The Doctor wasn't sure how it was possible, but she was even more beautiful than usual.
River turned and smiled upon seeing the Doctor's face. "I do like seeing that look on you."
He scrunched up his face then tried to arrange his features into the most innocent expression possible. "Wha… What look?"
"You know," she said playfully, "that look you get when you think I'm especially sexy."
The Doctor blushed and turned his attention to the basket in his hand as a distraction. He removed the cloth from the top and unfolded it then spread it on the ground. River settled herself on the blanket and was surprised that it was much softer than it appeared. Although it was no thicker than a bed sheet, it felt rather like sitting on a heavy down comforter.
He took a silver chalice from the basket and used it to scoop some of the light. The strange substance, somewhere between a liquid and a gas, crackled and sparked against the curved metal causing it to tarnish slightly around the rim. He placed it on the center of the blanket as he sat next to River. As he grinned at her, he reached into the basket and pulled out a bottle of wine.
"Wine? But you hate wine," River remarked.
"Yes, but you don't." He popped the cork and took a single wine glass from the basket, filling it for her. "Besides, I think you'll find this a little more special than the average wine."
She took the glass and looked at him questioningly before taking a drink. It tasted like the first wine they had ever shared together. Or rather, the first wine the Doctor pretended to drink as she enjoyed hers. Oh, what a night that was. But how could he know? That was in his future.
Reading the astonishment on her face, the Doctor said, "Have another sip."
River raised the glass to her lips again as the Doctor watched on with an expectant, almost giddy expression. As it touched her tongue, she nearly choked from surprise. It no longer was the wine of that special night so long ago. It now had the rich sweetness of strawberries and cream, which was a whole different extraordinary night in the Doctor's future.
"See? Told you." He winked at her.
"Have a sip," River said as she held the glass out to him, but he hesitated. "Just a sip, I want to know what you taste."
The Doctor gingerly took the glass as if it were poison and sniffed it. No matter its other qualities, it still smelled like wine. With some trepidation, he took a sip. "Fish fingers and custard," he admitted sheepishly as River laughed. He drank again, a little more this time. He turned several shades of red and shoved the glass back to River, causing a little wine to slosh out onto the blanket.
"Well? What was it?"
"What? What was what? Oh, er… nothing… nothing at all! Um… well... fish fingers. And custard. Again. Yes." He tried to look anywhere but her.
"Mmmhmmm," said River as she watched him fidget nervously under her gaze. Whatever he tasted, it embarrassed him even more than she usually did herself. She knew it wasn't the time to push him further, so instead she placed her hand on his, smiling gently at him. It seemed to calm him some.
They sat quietly together for a while before River spoke again. "You're enjoying this, aren't you?" She took another sip of wine, sighing happily to herself as the subtle taste of the Doctor's kisses washed over her.
"What? Being with you? I always do."
"I mean this, all this." She waved a hand around the area. "Showing me all these amazing things I don't even know about."
"Well, you have had the advantage there so far." He placed a finger against her lips as she looked at him questioningly. "Spoilers," he whispered. The Doctor moved his hand from her lips and ran his fingers through her hair, twirling her curls around his fingers. He traced a finger lightly around her earlobe before brushing his hand down her neck. Once at her shoulder, he gently nudged the strap of her dress so it slid down her arm.
"Look who is being a bad boy," River said silkily.
The Doctor giggled nervously as he blushed at his boldness. River loved that she could make him blush so, all the way back to when she first met him. Not that it was difficult, but she enjoyed it all the same. He was always so awkward when they were close like this, even if he tried to pretend he wasn't. It was one of those things she found adorable about him.
He dipped a finger in the chalice and traced it along her collar bone, nudging the strap from her opposite shoulder as he did so. She moaned softly and leaned into his touch. Her dress dropped a bit, still covering her but revealing more cleavage than before.
The Doctor felt his confidence waver. For once, he wanted to show her he could take the lead, but he was never very good at that sort of thing. Not when it came to romance. So far he had been quite impressed with himself. But that look in her eyes, the desire in her voice, his racing hearts, all made it very difficult to maintain his resolve.
Sensing his hesitation, River dipped her finger in the chalice and traced it lightly around his earlobe and along his jawline, dragging her fingernail along for added effect. He inhaled sharply against her touch and the tingling of the fluid.
With a slightly trembling hand, the Doctor swirled his finger across the surface of the liquid and ran it across her lips. River drew his finger into her mouth and shivered at the sensation of the remains of the liquid light on her tongue. As she sucked gently on his finger he went weak and his mind became foggy. A vague thought occurred to him that it would be even more wonderful if something other than his finger were in that lovely mouth of hers.
"How do you always do this to me?"
"Push me so much further than I think possible."
"Hmmm, I wonder how much further it would push you if I did this…" River picked up the chalice and tipped it against her lips. She shuddered then pulled him close and kissed him deeply. It was like an endless explosion between them. River's hands found their way to the buttons of the Doctor's shirt as they fell back together. The chalice and wine glass rolled across the floor, spilling their contents. The two substances sparked wildly as they mingled, sending off flashes that reflected against the crystalline surfaces of the cavern like fireworks. As the glow blanketed their entwined bodies, they knew that although all of time and space was open, there was no other place they'd rather be.