Title: Locked Lips

Author: Mindy

Rating: K+

Disclaimer: I own stuff but not them.

Spoiler: "The Unicorn and the Wasp".

Summary: Ten/Donna. Chemistry is undeniable.

A/N: For those who wanted a sequel to "Kiss and Tell", this is more on the same subject.

-x-x-x-

"What--?!" Donna pulled back abruptly, her hands on his arms, her face aghast. "What was that?" she demanded.

"Ah…" the Doctor froze in place, eyes wide: "thatwas a kiss. Don't kill me."

She pushed his hands off her. "What do you mean 'a kiss'?!" she spluttered: "What do you mean 'kill you'?!"

He spread his palms, taking a defensive step back: "Okay then, don't slap me."

She glanced up at him, swiped her fingers across her lips. "I should," she insisted mulishly.

He gulped anxiously. "Please don't."

"You can't just go around randomly kissing people when they're not prepared," she muttered, blue eyes flashing in the dim light: "I was in the middle of running for my life, if you didn't notice."

"It just happened," he winced. "It was an impulse, a mindless, unexpected reaction…."

She narrowed her eyes at him: "I know what an impulse is, dumbo."

The Doctor turned, gesturing wildly to the danger they'd just escaped from. "Things were exploding. We were running, we got separated. I wasn't sure if you were okay. Then I saw you and--" his eyes ran over her dirty clothes but intact body: "quite obviously, you were. We hugged--"

"Yes," she hissed: "I was there for that bit."

"I'm sorry," he shrugged meekly: "I was happy. Now, I'm scared."

Another explosion sounded above the tunnel they were taking cover in. The Doctor instinctively urged her further inside. Normally, he would put his arm around her, but this time, he didn't dare. He shuffled a little closer, acting as her personal shield. Donna ducked her head, covering her ears til the noise subsided.

She glanced up at him in the hazy half-light. "Well," she sighed, when silence descended again: "I s'pose that makes us even, at least."

The Doctor was looking up at the iron ceiling, listening intently for more explosions. "What d'you mean?"

"I've kissed you once," she muttered, gesturing between them: "You've kissed me once."

The Doctor's mouth turned up in one corner. "Right, exactly." He nodded, leading the way deeper into the cavernous, iron tunnel. "And it was no big deal, right?"

"Right," she agreed, following closely behind.

"In fact," he continued lightly: "as far as kisses go--"

"What?"

"Well," he sniffed and made a face: "they weren't entirely rubbish--"

"Thanks," she replied sourly.

"Hey," he scoffed, waving a hand at her: "I'm sure they weren't the best you've ever had either."

Donna aimed a glare at his pin-striped back: "What's that s'posed to mean?"

"Not that I'm saying that's your fault," he went on, oblivious and distracted.

"Oh, that's big of you," she muttered sullenly.

"No-no!" he insisted, turning to walk backwards: "I'm sure you're a very decent kisser. Really! Honestly, Donna, I mean that."

Donna stuck her chin out at him and commented coolly: "Sadly, I can't return that compliment."

"All I'm saying is…" he stopped walking, his tone placating: "both times were rushed…I wasn't expecting it the first time…you weren't expecting it this time--"

"That's for sure."

They'd come to a junction, one tunnel splitting into two. Donna slushed past him in the deepening mud. She peered down the grimy right tunnel then down the equally grimy left tunnel.

"I mean, think about it, Donna," the Doctor went on, standing in place in the mud, his mouth once again running away with him: "Everything we do together, we do well. Am I right? And if we were to try again--"

She turned on him, one finger raised: "Which we won't."

"Yes, no--" he shook his head then nodded it: "but, theoretically-- if we wanted to--"

She shot him an arch look: "Which we don't."

"I know," he huffed: "I'm just saying… if we took our time..."

Donna continued pacing. "Like a century or so?"

"If there were no wasps, no bombs…"

"Like that'll happen."

"I'm sure we'd be good at that too," he mused, seeming to reach the end of his speech: "More than good."

Donna turned to him, an assessing expression on her face. "And why's that then?" she asked after a moment.

"Well…" he answered hesitantly: "it just stands to reason, doesn't it?"

"Does it?" She blinked at him, hands on hips: "Explain to me why you think a third attempt would succeed when the first two quite obviously failed?"

He eyed her warily. "Speaking theoretically?"

She spread her hands in an exasperated gesture. "What else?"

"Well…my theory is very simple, Donna," the Doctor began imperiously.

Her eyes widened. "Is it?"

"Amongst other things," he put a hand over one heart, informing her: "I am a scientist."

Donna looked unimpressed. "If that's a fancy way of saying nutjob then, yeah."

"See…" he continued, closing the space between them and leaning in to share his wisdom: "it all comes down to one thing."

She folded her arms, watching him intently. "Which is?"

The Doctor grinned. "Chemistry," he told her after a moment: "Some people just have it."

Donna bobbed her head a few times, waiting for more. "That's your theory? Your entire theory?"

"That's it," he replied with a resolute nod: "That's my theory."

She flicked a finger between the two of them, unable to fully suppress her smile. "Chemistry?"

He nodded, eyes aglow in the murky light. "Indestructible and undeniable."

Donna regarded him skeptically for a moment then turned on her heel. "Obviously, you've never seen me in denial," she remarked, choosing to slosh down the right tunnel.

The Doctor traipsed after her. "I think I might have," he commented under his breath.

"Doctor?" she sang.

"Donnaaa?" he mimicked back.

She threw a look over her shoulder. "Want to know what I think?"

He dipped his head. "Always."

"Why we've never properly locked lips?" she asked, her tone sweetly ominous: "And aren't ever likely to?"

"As a scientist--" the Doctor began.

"Nutjob," she interjected.

"And as a man," he added, unfazed: "I'd be very curious, yes."

He ducked ahead of her to prop open a heavy, rusted door. Flashing her a lopsided grin, he waited for her to pass underneath his outstretched arm.

"My theory is very simple, Doctor," Donna announced smoothly, laying a hand over her heart: "Amongst other things, I am a woman."

"Also undeniable," the Doctor's grin increased, his hair falling over his forehead: "I had noticed."

"And you," she ducked under his arm, pausing to glare up at him: "don't know when to keep your mouth shut." She emphasised her words with her fingers, making a little locking gesture over her lips.

The Doctor caught her arm before she could step over the threshold. "It's very lucky we're so rubbish at it then," he murmured. He tipped his head at her: "Isn't it?"

Donna studied him a moment then rolled her eyes. "Case and point."

The Doctor watched her pass then shook his head. "….Damn."

END.