A/N: Demon!lock that was originally a prompt and has turned into a bit of a series. I actually wrote this as a prequel to the story "A Devil of a Time" which I will also be posting here (both are already on AO3). There will likely be another one at some point in the future. Just FYI, the demons in my world are non-Christian in origin, and were trapped in our world when they crossed over from a different dimension. And this world has loads of other magical beings as well! Rated for smexy times and some, um, anatomical differences that demons have, mostly regarding shapeshifting, tongues & tails. So, yeah, a bit on the...kinky side.

"Molly, I have a bit of a favor to ask you."

Molly Hooper, youngest pathologist on staff at St. Bart's Hospital, turned to face her supervisor, Dr. Mike Stamford, a politely inquisitive expression on her face. "If it's about Mrs. Sondheim in Drawer 17, Bob the security guard already said he'd be willing to pay for the reanimator to bring her back," she joked.

Mike grinned but didn't look any less uncomfortable than he had before she said anything, which was mildly alarming as he usually guffawed at Molly's morbid (and borderline inappropriate) sense of humor, so she just asked, "What is it, Mike?"

"There's someone coming in today to look at a body – Mrs. Sondheim, as a matter of fact – at the request of the Met. Ah, a DI Lestrade made the call," he added. Molly nodded and waited for him to get to the point; she'd shown bodies to the police before, so why was this request any different?

"Err, the thing is, DI Lestrade will be bringing someone with him when he comes in…a sort of private consultant by the name of Sherlock Holmes."

Molly nodded; so far nothing Mike said made a lick of difference to how she would deal with things. A private consultant on a police case was new, but why would Mike seem so concerned about…

The penny dropped and Molly stared at Mike, alarmed and excited. "Is it a Supernatural?" she asked. "Is that why you're acting so – I mean, is that why you're worried about me?"

Mike nodded, appearing relieved that Molly had figured it out on her own – and wasn't freaking out about it. But why should she? She'd grown up with a weather witch as a next door neighbor, and a best friend in school all the way to uni who'd been a half-demon. And there were thaumaturges on staff here at St. Bart's, as well as various types of supernatural Healers and Empaths.

"Not everyone is comfortable working with demons, even with the Equality Act and all," he explained nervously. "Not that I'm accusing you of prejudice, you know I'm not doing that, at least I hope you do!"

Molly shook her head and gave him a reassuring smile. "No, I get it, Mike. You just wanted to make sure I'd be all right with a Demon in the morgue and I am, it's fine, it really is. Let's just hope he doesn't mind working with a Human pathologist!" she joked.

Mike finally grinned and shook his head. "Oh, I think you two will get along swimmingly!" he predicted.

oOo

Molly thought back on that first meeting with a mixture of fondness and exasperation. Sherlock Holmes had appeared, much to her secret disappointment, in his fully Human form. Not so much as a single scale on his skin or a pair of horns peeking from between his lush head of dark curls. Not that she had any complaints about his Human form; on the contrary, she'd nearly drooled at the sight of him as he accompanied the older man her co-worker Meena dubbed 'The Silver Fox', who of course was DI Lestrade.

Sherlock Holmes in Human form was six feet of gorgeous, lean intensity with heterochromatic eyes that Molly could have stared into for hours if he'd let her. His cheekbones and lips were just as beautiful, the one sharp enough to cut herself on and the other plump and kissable, lush and pink, perfect Cupid's bows she longed to taste.

Then he'd opened his mouth, and oh! That voice! A heady baritone, velvet over steel that hardened her nipples and weakened her knees. Luckily she wore layers – bra, blouse, jumper, lab coat - and was leaning against an autopsy table when he first spoke, although she knew his keen senses would easily sniff out her instant arousal. But then, she consoled herself, he must be used to that kind of reaction from people. At least she acquitted herself well enough once she became absorbed in reciting the details of Mrs. Sondheim's death and explaining – and sometimes defending! – her findings to the detective and the consultant.

All in all, she considered that first meeting a good one, even if he'd snipped at her regarding her fashion sense and argued with her over several details of her autopsy – details which, eventually, he'd grudgingly agreed she'd actually got right.

The moment she'd been exposed to that brilliant, diamond-sharp mind, she decided later, was the moment she'd tumbled head over heels in love with him.

The moment he'd conceded that she actually knew what she was doing, he would later reveal, was the moment he'd decided to pursue her as a romantic partner, although the idea of taking her as his mate would come a bit later.

He'd certainly wasted no time in deciding to act on his interest in her; two hours after he and DI Lestrade had left together, Sherlock returned alone, unwinding his scarf from around his neck and dropping it over Molly's shoulders before she even realized she was no longer alone in the morgue. "Sh-Sherlock? What are you…"

She couldn't finish the question because he'd grasped her by the upper arms, lifting her from her chair, and kissed her. No, not just kissed her; snogged her properly, mouth open, tongue demanding entrance to her mouth, arms holding her tightly against his body. Molly hadn't even tried to push him away, melting into his embrace, eyes snapping shut as she returned the kiss wholeheartedly.

When it ended – she needed to breathe even if he was still perfectly fine, stupid demonic lungs – she stared at him before blurting out the first thing to come to mind. "So…you caught the murderer, then?"

Sherlock laughed, shook his head, and kissed her again, just as thoroughly as he had the first time. "Yes," he said, when that kiss ended, reaching up to tug Molly's hair free of the elastic that had been holding her ponytail in place. "We caught him. Thanks to you, I didn't go off on a wild goose chase after a false clue. I told Lestrade that you were the only pathologist I would work with from now on," he added casually as he reached out and began unbuttoning her lab coat, careful to leave his scarf draped over her shoulders. "And Mike knows not to let anyone down her for the next couple of hours."

"Why…why not?" Molly whispered, although she had a very, very good idea she already knew why. As Sherlock removed his coat – an expensive black Belstaff – she saw exactly what she'd hoped to see: a very nice bulge in the front of his neatly pressed black trousers.

"It's technically against the rules for us to copulate in such a public area of the hospital, but Mike owes me a favor or two and I told him this covers all of them," Sherlock replied, his voice going just a shade deeper. He grinned as Molly let out a low moan of desire, his thumbs caressing her cheeks as he held her face in his hands. "But I want to mark this as ours. What do you think, Miss Molly Hooper, Specialist Registrar?" Brushing his lips against her forehead, he murmured, "Are you willing to let a demon fuck you on a freshly sterilized autopsy table?"

"I don't have anything for the Burn," she replied, startling another delighted laugh from him.

"I'll stick to Human form, unless you'd prefer seeing me in my demi form?" he said, stepping back from her long enough to continue removing his clothing, blithely unconcerned with the CCTV cameras mounted in the four corners of the room. But then, he could always have the footage deleted, she supposed, and it wasn't as if there was anyone actually watching it live…

"Fuck it," Molly muttered, throwing caution to the wind and fumbling with her jumper, pulling it over her head before attacking the buttons to her colorful blouse. When she looked up again, she gasped; Sherlock was completely naked, proudly erect, his body hairless and pale as an Elgin marble, and just as classically sculpted. As she watched, nearly panting with desire, he began to transform into his demi-demon form, still safe for a Human to touch without magical protections.

Touch, mmm, yes. Touch, kiss, taste…she could hardly wait.

Within seconds Sherlock's already pale skin had taken on a ghostly sheen, the pearlescent white scales covering him glimmering softly in the bright fluorescent glare of the overhead lights. His canines formed into fangs; his eyes took on an inhumanly bright azure hue as their cat-like slant became even more pronounced, and two obsidian horns, slightly curving over the back of his head, erupted from his dark curls. He had no wings in this form, but she caught a glimpse of a long, slender tail topped with a blunted version of the usual demonic barb before being distracted by his next words.

"Well?" Sherlock asked, his voice a slightly deeper, huskier version of how he sounded in his fully human form, with a bit of a growl deep in his throat behind every word. "What do you think?"

Molly answered not with words but by virtually hurling herself into his arms, eager to feel his transformed body against hers. Yes, she wanted to have sex with him in his fully human form and eventually in his fully demon form but this one just did things to her; his cheekbones were much more pronounced, his cock a bit larger, and the prehensile tail he lazily wound about her legs, the blunted tip brushing teasingly against her pussy…yes, that freshly sterilized autopsy table was about to be put to a very different use than it had been designed for.

Their lips crashed together in a fierce kiss; she felt his tongue thickening a bit inside her mouth, and remembered that a demon's tongue could alter in shape and size until it was virtually a human male's cock. But before she could even think about worrying about choking, she felt it shrink back down before Sherlock pulled away. "Sorry," he murmured as he began undoing the rest of the buttons on her blouse, lowering his head to press a series of sucking kisses to the side of her neck. "Got a bit carried away there."

"It's all right," Molly gasped out, clutching his dark curls in one hand and grinding her hips against his. Then he scraped his sharpened teeth against her carotid, a teasing move that promised untold pleasures, and Molly nearly collapsed as a shudder of pleasure shook her small frame. "G-gives tongue-fucking a whole new meaning, I guess," she moaned out without thinking, then blushed as he chuckled and lifted her onto the autopsy table.

"Mmm, yes it does," he replied as he eased her trousers and knickers off her body – she'd already kicked her shoes off and wasn't wearing socks today. "Say the word and I'll be happy to give you a demonstration of just how…skilled…I am at that particular activity."

Molly, who had been fumbling with the hook-and-eyes to her back-closing bra (time to invest in some front-opening ones!), gasped and squeaked out a, "Yes, please!"

With another dark chuckle, Sherlock hopped up onto the table with her, kneeling between her legs while she slid herself back a bit to give him more room. Then she leaned up on her elbows, staring down as he moved with a sinuous grace, dipping his head down after flashing her a wicked smile that showed every single one of his pointed teeth.

Not a single one of those teeth so much as grazed her as he lowered his mouth to her body, kissing his way along her thigh before delicately running his tongue along her slit. Molly's head fell back on her shoulders, her hair brushing the cold metal surface that was in such contrast to the rising heat of her flesh. She panted and twitched as she felt Sherlock's thumbs sliding along her opening, widening it as the soft swipes of his tongue became harder, more passionate. And when he suddenly thrust his tongue inside her, thickening it until it filled her as much as any previous boyfriend's cock had, she couldn't stop the guttural moan from erupting from her throat.

Just as she was about to come he pulled back and gave her thigh a sharp nip. "Ow!" Molly yelped, glaring down at him. "What was that for?"

"Marking you," he replied distractedly as he thrust his thumb into his mouth and bit down hard enough to draw blood. While Molly watched, eyes wide and mouth dropped open in shock, he smeared the blood over the toothmarks he'd left. Instantly she felt a flash of heat, followed by icy cold, and yelped again, twitching a bit before the sensations eased. The Mark vanished into her flesh, and she knew it would be invisible to purely human eyes but quite clear, even through her clothing, to any magical being. It had started off as a property Mark, back in the days when demons owned human slaves, but in these modern, enlightened times, it was more of a social convention, a visible way of showing that this human – herself – was involved with a demon.

It meant that Sherlock wanted more from her than just a quick shag in the morgue. The Mark wasn't permanent; it would fade over time if not renewed by the same methods or bespelled by a wizard. But for him to have bitten her at all, so soon after they'd met…

"Molly, don't take this the wrong way, because I promise I am not actually telepathic, but you are thinking too loudly," he said, interrupting her racing thoughts. "I just wanted you to know that I'm interested in you for the long term. Seemed like the quickest way to reassure you of that," he added, sounding a bit uncertain. He peered up at her, still resting between her thighs. "Not good?"

"Oh, no," Molly hurried to reassure him. "Very good. Very, very good." She tugged at his hands and he willingly slid up her body, taking her mouth for a hungry kiss. She didn't bother with anything fancy, just reached down between them and took his prick in her hand, guiding him to her opening as she widened her legs.

His tongue had been amazing; his prick was a bloody miracle, and she gasped that out as he began rutting into her. She bent one leg to give him a better angle; he groaned his thanks and dug his fingers into her hair as he rested his forehead above hers. She felt some ghosting over her breasts and peered down to see his tail moving sinuously from one to the other, teasing her nipples even more fully erect with every touch.

She moaned, turning her head and tugging at Sherlock's earlobe with her teeth, nipping gently and then harder as he groaned and began fucking her with even more urgency. "Fuck," he gasped out, his lips against her throat as she continued to nip and nibble. "Keep doing that Molly, don't stop, don't stop, please…"

His mumbled words were no longer comprehensible to Molly's purely human ears, as he fell into demon-speak the closer he came to his peak. The low murmuring with its guttural undertones that fell just into the human hearing range sent a shiver through her body, and she cried out her completion only minutes before he roared out his own.

While she was still waiting for her breathing and heartrate to get back to normal, Sherlock pressed a kiss to her lips and hopped off the table, instantly transforming to his fully human form. "Hurry up and get dressed, Molly," he ordered, tossing her clothing at her while rapidly donning his own. He was fully dressed and tapping his foot impatiently while she was still fumbling with her knickers and bra.

"What's the hurry?" she asked. She knew demons were known for cuddling, and hadn't expected him to continue to hold her afterwards, but Sherlock's current behavior was confusing her. "You said Mike would make sure no one interrupted, and it's only been…"

"Yes, yes," he said, cutting her off and yanking on her foot so he could put her sock on. "But I don't want the next time to be so hurried. We're going back to mine so we can be guaranteed privacy." He paused, holding one of her shoes as he rolled his eyes. "Relative privacy. I'm sure my landlady will be thrilled that I've brought a woman home."

Molly wasn't quite sure how to respond to that, but settled for continuing to get dressed as Sherlock whipped out his mobile and began texting furiously. She still had an hour left to her shift but had the feeling Mike wouldn't mind if she ducked out a bit early; she certainly had enough vacation and personal time saved up!

"All settled," Sherlock said, sounding satisfied. He placed his hands on Molly's waist and lifted her off the table and onto the floor, kissing her as she tried to blindly slide her feet into her shoes. "John – my flatmate, John Watson – will stay at his latest girlfriend's flat and Mrs. Hudson – my landlady – will be staying with her sister for the weekend." He gave Molly a wicked grin that curled her toes and stole her breath. "So we'll be quite undisturbed for the next couple of days. I do hope you're feeling well rested, Miss Hooper? Or have I quite worn you out?"

"Oh, I think I'm up for a few more rounds," was her cheeky reply. He gave a startled, appreciate laugh and caught her up for another kiss.

"Good," he replied, nuzzling her throat. "Because I am feeling very, very energetic at the moment. Meeting you has definitely made this day infinitely better."

His words gave Molly a warm glow, and she happily left the room with him, her hand tucked into his arm as she looked forward to whatever their relationship would bring them.