A/N: For the prompt - The Librarians AU with Helen as guardian

A shadow loomed over Nikola's path.

The shadow belonged to Helen Magnus, who was hacking aside bits of jungle in front of him, and she presented quite a striking silhouette. Of course, Helen was always striking with a weapon. Her hat was pulled low over her eyes, the machete in one hand, and her –

"Nikola, please tell me you're not internally narrating again."

Nikola stopped in his tracks and fixed her back with an offended look. "Of course not! You insult me, Helen."

She turned around to smirk at him. "Good. Because I would hate to think that after days of trekking through the jungle, complaining at me every single solitary second about the bugs, and the heat, and the humidity, and all the wine you're not drinking…"

"Yeah, yeah, I get it," Nikola said.

"…After all that, you're too busy staring at me to see that we've arrived at our destination."

Nikola's eyes widened, and he hurriedly caught up to Helen, standing at the top of a small rise. Once he was next to her, he could just barely see an engraved stone column through the brush and trees. "Oh my God," he muttered, and started running towards it.

"Nikola, wait!" Helen's exasperated voice rang out from behind him as she took off in pursuit.

He caught himself after a stumble in the underbrush and skidded to a halt beside the stone, staring up at the column with his mouth open. It was crumbling, beaten down by age, though the signs cut deep into its surface remained nearly untouched. To his left, a cavern gaped open, and he could feel the cooler air within even from where he was standing. "I don't believe it. The ancient script of the Sanguine Vampiris… Helen, take a look at this!"

She caught up to him, looking annoyed. "I'm trying. If only someone wouldn't go running off all the time…"

Nikola ran a hand over the weathered stone. "Sure, sure," he said absently. "I know, I'm the most annoying Librarian in the history of the universe, created solely to test your patience."

Helen looked at him practically melting into the rock with fond amusement. "Should I leave you alone with that?"

"Oh, Helen, there's no need to be jealous – you know you're the only one for me."

Helen pursed her lips, rolling her eyes. She put a hand over her forehead, shading them, while she looked at what they could see of the sky through the thick green jungle foliage. "It'll be dark soon."

Nikola looked up. "Huh. Time flies when you're about to die from over-exertion." He could hear Helen chuckling. "Hey, thanks for the sympathy."

Naturally, she ignored him.

"I'd love to take a closer look at this before we head in," he said, looking at her pleadingly.

His tone was apologetic because the cave was technically their official destination. It was supposed to house an ancient vampiric artifact that, according to their source, "held unknowable power." Of course, their source had been a little drunk when he'd said that (or a lot – Nikola could drink anyone under the table), but it was still as good a lead as they'd had in weeks, and Nikola knew he and Helen were both eager to find something.

Helen raised her hands in a "do whatever you want" gesture. "Very well. Take your time."

Nikola grinned at her. "I love you."

She smiled back at him. "I know."

It was almost dark by the time he'd finished – he'd taken longer than anticipated. Helen didn't seem to mind, throwing him frequent glances as she waited, pacing back and forth or leaning against a nearby tree trunk.

Nikola always loved the feeling of Helen watching him protectively. Sure, as his Guardian, it was her job, but they'd been together for a long time, longer than most would guess, and their original roles had begun to blur together with time. Helen was essentially a Librarian herself, and as she pointed out with regularity, Nikola had a reckless streak of self-sacrifice when it came to her that would have made him a fine, if short-lived, Guardian.

Regardless, there was a part of Nikola that secretly (and sometimes not so secretly) thrilled at someone as brilliant and wonderful as Helen choosing to spend her time looking after him.

That and she looked hot with a gun.

"Are you about done?" she called, apparently sensing him drifting away from any useful train of thought.

"Just finished," he replied, tucking his notebook back into his jacket..

Helen came over to stand next to him by the stone. "Glean anything useful?"

"This was built in the reign of Queen Afina," Nikola said, wandering over to the mouth of the cavern and staring down its pitch-black abyss. "That contains a history of her achievements. Potentially we could fill in some of the gaps in her history, but I'll be able to tell more when I have more time."

A strange sound emanated from the mouth of the cavern: steady rustling beats, getting closer by the second. Nikola leaned in, trying to identify it, and had almost made out a shape in the darkness when he was tackled from the side and shoved to the ground with Helen on top of him.

Before he could do anything, a storm of bats flooded out of the cave and into the darkening sky, the sound of their wings rushing over them. A few moments later, they were alone again.

"Careful," Nikola said, grinning. "They might circle back to suck our blood out."

Helen rolled her eyes. "Joke all you want, but one of these days, you'll stick your nose into something less harmless."

"Well…" Nikola's arms were pinned to his sides, but he managed to reach a hand up and touch her elbow. "That's why you're here."

She shook her head, getting up and offering him a hand. "It would be a good deal easier if you didn't go poking around in dark caverns so frequently."

Still grinning, he took her hand and stood up. "You wouldn't like me if I didn't poke around in dark caverns. Besides, when have I ever been overly reckless in the field?"

Helen snorted loudly and started into the cave. "Oh, please. Vienna?"

"It was a temporal instability!" Nikola said defensively, following her. "Nothing I did counted anyway."

"Egypt."

"Well, in my defense, that tomb was really cool."

"Italy?"

"I had that completely under control."

"Canada."

"...Ok, you might have me there."

"Canada again."

"Fine, fine, I get the picture…"

It was even darker inside the cave. The passage was large, large enough that the flickering light from Helen's torch didn't quite reach from one side to the next. They walked side by side, Nikola stopping occasionally to read the inscribed pillars lining the tunnel.

"Anything more of interest?" Helen asked as he turned away from the latest.

"Oh, you know, the usual," Nikola said cheerfully. "Death and torment await anyone foolish enough to venture here. I'm guessing the vampires kept something really cool here."

"If by 'cool' you mean 'potentially world-ending,' I assume," Helen said.

He shrugged. "Same thing."

Nikola had turned to face Helen as they walked along, and neglected to watch where he was going. On his next step, instead of landing on the uneven stone floor of the cavern, his foot came down on nothing at all; he lost his balance and tipped forward. For a moment he was suspended in midair, trying to regain his balance but unable to do anything but sway wildly.

Then, swearing, Helen dropped her torch and threw both arms around him, hauling him back from the edge of the drop-off. The torch fell, clattering to the stone below with a soft thunk, and illuminated the sharp spikes standing straight up from the rock. They gleamed in the orange light, made of some sturdy metal that had endured for centuries.

"Ouch," Nikola said breathlessly, very glad of Helen's steadying arms around him. Behind him, she exhaled sharply, resting her forehead on his shoulder in relief before she released him and stepped back.

"Don't let go on my account," he said, though his grin was a bit unsteady this time. He pulled a flashlight out of his jacket pocket and handed it to her, taking care to keep well away from the crumbling edge of the drop-off.

Helen trained the beam over the gap in the floor, easily twenty feet across, with those deadly spikes lining every inch of the pit underneath.

"That's unfortunate," Nikola said.

"Not to worry," Helen said, handing the light back to him and digging around in her backpack. "I came prepared."

"Please tell me you have a whip in there." Nikola leaned over her shoulder to get a look.

She rolled her eyes before standing, holding up a disappointingly ordinary coil of rope. "Only rope, I'm afraid."

"Well, that's fun too."

Ignoring him, Helen stepped closer to the edge of the pit. Nikola winced, but she kept her feet as she tossed a loop of the rope high up in the air. He kept the beam of light focused on the ceiling, where she had neatly landed the rope around an outcropping of rock. She pulled it tight, and the loop closed around the stone.

"Keep the light on the opposite side," she said, gesturing for him to move back.

Nikola eyed the rope warily. "Is that gonna hold you?"

Helen shot him a smirk. "Only one way to find out."

He watched in admiration as she swung over the pit, landing smoothly on the other side and straightening to look back at him.

"Throw me the rope and I'll throw you the idol!" he called out, grinning and a bit relieved.

A chuckle was his only answer as she tossed him the rope. Nikola's crossing was far less graceful, but he arrived unscathed at the opposite side and stumbled into Helen's waiting arms. His balance returned quickly, but he saw no reason to step away before she did.

"Any excuse to hold me today, I see," he whispered in her ear.

The expression on Helen's face as she immediately let go of him and moved away told him she was about to say something like "Nonsense," or perhaps "Bloody hell."

"Oh, bloody hell," she said.

Nikola's grin faltered. That hadn't been his "bloody hell," the fond one Helen reserved for when he was being particularly exasperating. That was the one she used in tight situations where something had gone wrong.

She nodded towards the gap. "We've left our rope behind."

Sure enough, it was hanging out of reach of either of them. "Well, surely there's bound to be another way out of here," he said.

"Let's just hope it's still useable."

"Aw, does being trapped with me for eternity sound that bad?"

Helen just rolled her eyes.

The passage climbed sharply after that. Soon, they were hiking up a steep incline, and within a few more minutes light was visible at the end. The cavern widened as they approached the light until they reached the end of the passage, where a high arch and massive stone doors loomed.

It took both of them to move just one of the doors, heaving with all their strength until it finally slid a little way open with a heavy grinding noise. Helen slipped through first, then beckoned Nikola in.

He joined her. If it hadn't been for her cautioning grip on his arm, he might have run forward right then and there.

They were in what was no doubt one of the central rooms of the fortress. It was close enough to the surface that Nikola could see small shafts in the walls that would have let light in, if it had been daytime. A carved stone platform rose in the center of the room. On it was a crown, made of shining silver with dark red gems glittering in it. It seemed untouched by age or dust.

Nikola's breath caught. "The crown of Queen Afina," he whispered. It was believed to give the wearer the powers of the ancient vampire queen herself: enhanced strength, speed, and healing. But it had been lost for thousands of years.

Not anymore. Nikola tried to take a step forward, but Helen held him back again.

"Nikola, look there." She gestured at the wall. There were tiny holes lining it all the way to the end of the chamber where the crown was. Slowly, she stooped and picked up a loose stone from near the door, and tossed it forward.

They both sprang back immediately as narrow, brilliant beams of purple-white light shot out from the walls. The stone hadn't even reached the floor before it had disintegrated completely.

Nikola's eyebrows shot up. "Ouch," he said again.

"Indeed," Helen agreed. She threw another stone with the same effect.

"They all fire at once," Nikola said, narrowing his eyes.

"No rhythm," Helen said, then shot him an amused look. "If that's what you had in mind."

He shrugged, offering her a grin. "You, me, the Amazon rainforest…" He gave a sigh of reminiscence. "That was our first dance."

Her lips quirked, but she turned away and picked up two more stones, throwing one just after the other. The second clattered safely to the floor, the beams firing a split second too late to catch it.

"There's a three-second delay while they recharge," she pointed out.

"Three and a half," Nikola said.

"Think you can make it?"

He offered her his arm. "Only one way to find out."

It was a symbolic gesture, of course – they would each need to be running as fast as they could, and holding onto each other would only slow them down. But Helen gave him an almost mischievous grin, and picked up another stone.

"On my mark," she said, stepping to the edge of the trap's field and readying herself. "Ready?"

Nikola nodded.

As soon as the beams shut down, they took off across the chamber. For Nikola, time seemed to slow; he counted each fraction of a second even while he pushed his legs to go faster. Helen outstripped him, reaching the opposite edge while he was still several strides away.

She began to turn and Nikola realized he wasn't going to make it; with one last desperate effort, he dived forward right before the beams flashed on, tumbling onto the stones at the foot of the crown's pedestal as they fired behind him.

Nikola collapsed in relief against the floor, groaning. Then, he struggled to his feet, glancing over at Helen.

"Unscathed?" he inquired.

She nodded, breathing rather heavily. "Yourself?"

He grinned, looking back over at the trap. "Oh, with my usual awe-inspiring genius – "

"Nikola!"

He had never even seen the second trap; there was a sudden burst of light and a searing pain in his chest. At first it felt like he'd just had the breath knocked out of him, and then Nikola looked down and realized with a sort of dull surprise that quite a bit of his chest was missing.

"How about that," he said faintly, before his legs buckled. Helen caught him, sinking down onto her knees with him before the pedestal. For a few seconds he couldn't hear her over the insistent pounding in his ears. Then, dimly, her voice started to come through.

"Damn it, Nikola," she said roughly, her arms tight around him.

Then the pain hit, so strong that Nikola didn't even realize Helen had let go of him and was standing, carefully avoiding the stone he had stepped on, until she was already reaching out for the crown.

"Helen – no – " he croaked, certain that there would be some other trap, but nothing happened as Helen snatched the crown off the pedestal and knelt beside him again.

She dropped it onto his head none too gently, the silver circlet askew in his untidy hair. "Work," she hissed, and even though Nikola was feeling a bit sluggish, he could figure out that she wasn't talking to him. "Come on."

Nothing happened. She seized him by the lapels, but seemed to be lost for words: she bent her head until all he could see was her dark hair.

"Only a rumor after all," he mumbled. "Well… worth a try." Already exhausted, he let his head loll back against the pedestal.

"Stay awake," she ordered, and then her voice finally broke. "Nikola – "

"It's ok," he said softly, and with an effort, he reached up to touch her cheek. "Hey... at least you'll get a less annoying Librarian."

Helen gripped his coat a little tighter and leaned forward to rest her forehead on his. She didn't respond for several seconds; then, so quietly he could barely hear her, she whispered, "I'd rather have you."

Nikola smiled, and stroked Helen's cheek one last time, and closed his eyes.

Then he bolted upright, a sudden rush of adrenaline coursing through him. There was an odd jerking sensation in his chest followed by warmth flooding through the wound. He could breathe without pain again, and then he could move without pain, and then he looked down and realized that all of his chest was back where it should be, new pink skin quickly fading into a normal tone. Though, sadly, his waistcoat would never be the same.

Helen had pulled back, startled, when he first sat up; she quickly looked away, but he caught the flash of pure joy on her face beforehand.

"Wow." Nikola shook himself, poking at the hole in his waistcoat where there had been literally nothing only a minute before. "Well, these vampire artifacts really come through in the long run, don't they? Good thing, too. God knows what the world would do without me." He grinned at her, basking in the relieved looks she was giving him between glares.

"Don't try my patience," she warned, but then she seized his shoulders and kissed him.

A few enjoyable minutes later, she helped him to his feet. He didn't especially need help – he had never felt this good in his life. "I gotta say," Nikola said, taking the crown off and peering at it, noticing that the effects hadn't faded when he removed it. "I'm surprised the crown itself wasn't protected – "

Then the stones underneath them suddenly crumbled and fell away.

Nikola was falling before he even realized what had happened. The light from the chamber above was already receding, plunging them into total darkness. One of his flailing hands grazed the rough, rocky side of the shaft and he snatched it back, wincing and barely holding onto the crown.

To his side, he felt Helen give a jerk and heard her grunt, before her hand went limp in his.

"Helen!" he called, trying to twist around to get a look at her.

A blast of cool air hit them; Nikola looked down and saw a faint glimmering beneath them, before they both plummeted into cold water.

The surface struck him like a ton of bricks, driving most of the oxygen out of his lungs, before the water closed over them. Once they were submerged, Nikola found that he could see clearly through the murky water, even without light. He glanced down at the shimmering silver crown in his hand. Perhaps this was another perk?

Helen had drifted even further away from him after they hit the water – he looked around frantically for a moment before he saw her. Her eyes were closed, and she wasn't moving. With rising panic, Nikola noticed a small cloud of blood in the water above her head: she must have struck it on the side of the shaft on the way down.

He swam over to her as quickly as he could manage with the heavy crown still in one hand. She was sinking faster than he was, unconscious and unable to struggle against the pull of the water, but he managed to catch her arm before she fell away from him.

Then he looked up, and realized with a lurch that they were far deeper beneath the surface than he had supposed. Even as he began kicking, ascending slowly, he was running through the likelihood of success.

It seemed low. Even if he could make it to the surface, who knew how much water Helen had already breathed in? He had to readjust his grip on her arm, her soaked leather jacket slippery under his fingers, and when he was finished they had sunk back down nearly to where they had been before.

His lungs were burning, the water feeling heavier by the second. At that moment he wouldn't have put money on being able to make it to the surface himself, even if he let go of both Helen and the crown.

Nikola was only willing to give up one of those. Immediately, though not without a sharp stab of regret, he released his grip on the crown. He didn't even watch it fall away from him, turning to Helen to get a better hold on her, hooking one arm under hers and using his other to help pull them up through the water.

As soon as the crown was out of contact with his skin, he felt the effects: his limbs seemed feeble, the water dark and stinging his eyes. He couldn't see the surface now, so he closed his eyes and blindly hoped that he could make it in time.

But he could tell that he was ascending faster this time, now that he had freed up one arm. Lack of oxygen was making him choke, but he pressed on, until he finally broke the surface.

For a few seconds all he could do was hack water out. His vision was swimming by the time he managed to take a huge gulp of breath. He started coughing again as soon as he did, but it lightened the pressure long enough for him to get through the fit and take another breath, and then another.

He hauled Helen up to the surface, all his energy focused on keeping them afloat. Blinking the water out of his eyes, he spied what looked like land a dozen feet away: a slightly more stationary lump of black rising above the dark lapping waves of the underground lake. It was pitch-black above them – the floor must have reformed somehow in the crown chamber.

"Vampire technology," he coughed to Helen as he began to make his way over to the land. "Incredible, isn't it?"

There was a slight current in the water, thankfully working in his favor, and he reached his destination only a few moments later. Crawling onto hard and slippery stone, he pulled Helen out of the water and turned her on her side, balancing himself unsteadily on his elbow next to her.

His hands were shaking too much to take her pulse, but she was so still… Surely she should have responded by now. His stomach lurched.

"Helen," he whispered, pushing wet hair out of her face and stroking her forehead, trying to see if she was breathing. "Helen, my dear, can you hear me?"

As if she had, she gave a sudden, violent jerk and began coughing even more water onto the rocks beneath her, and a little onto Nikola.

He was too relieved to care (mostly), and shifted his arm to keep her steady while she coughed, her body racked with the force of it. When she was breathing more normally, she fell onto her back.

"And you didn't even give me a chance to do mouth-to-mouth." Nikola's tone was light and joking, but his hands were still trembling.

"Thank you, Nikola." Her voice was hoarse. Nonetheless, there was a small smile pulling at the corners of her mouth.

"Don't mention it." Nikola resumed his gentle stroking of her forehead. "I mean, you could mention it a little, because I was pretty heroic just now."

She laughed quietly, coughing a little more afterwards. "I'm sure you were a spectacle of nobility, my dear." She glanced around, taking him and their surroundings in.

"Where's the crown?"

Nikola winced. "Well, speaking of nobility…"

"You let it go?" she asked incredulously.

"Would you rather I let you drown?" he replied, a bit testy.

"No, I'm only surprised." Her voice was still amused, but soft. "An artifact of that power and age, all that history…"

"Yes, well, the artifact can breathe underwater. You can't."

Her eyes crinkled. "I believe that much was obvious." She lifted a hand, threading it through his hair, and pulled his head down to hers.

She was freezing cold, tasted strongly of dank cave water (the contents of which Nikola really didn't want to think about), and the kiss lasted all of two seconds before they both had to pull away to cough and take shivering breaths. Nikola had never loved kissing her more.

He lay back next to her, their fingers entwining, and closed his eyes, content to listen to her breathe and rest for a while. When they got their breath back, she sat up.

"I believe the water's flowing past us here," she said, straining to see into the darkness beyond where they sat. "Could it run outside? We did go up a considerable distance before we reached the inner chambers."

"It's possible." Nikola sat up too, still holding her hand. "It's not like we have much choice anyway."

"True," she said dryly. "Well, we may as well get started. Come on." With this, she rose and tugged Nikola to his feet.

"Careful," she warned as he slipped on the damp rock. "I'd rather not spend any more time in the water than necessary."

Nikola had been so concerned about Helen that he hadn't stopped to think about it, but the realization came to him now, looking at the rippling dark water.

It seemed unlikely that the ancient vampires, not exactly known for their mercy, would save the least deadly trap for the most serious crime. Something besides cold water must have been down here to make potential thieves regret their hubris. It was possible that whatever it had been was long dead; it was also possible it was only sleeping. Nikola thought it best not to find out the hard way.

"So much for getting the crown," he said glumly, staring at the water.

"Cheer up, Nikola," she said, patting his arm. "We'll come back later, when we're more prepared."

"I'll hold you to that."

"I would expect nothing less."

After what felt like hours of walking, clinging to the rock wall to avoid falling in the water (or, in Nikola's case, clinging to Helen's hand), they at last emerged into the jungle outside. The underground river had narrowed as they progressed until it was barely a creek. At the end of the tunnel, it flowed out of a small opening in a hillside and into a pond.

Nikola stumbled out with relief, falling into the water underneath with a loud splash before crawling onto the bank alongside Helen, who had insisted on going first.

"Well," he said to her, breathing a bit heavily. "Same time next week?"

Helen chuckled, turning her face to his. Her hand found his in the mud of the bank, and she said, very softly, "Nikola."

Nikola spoke almost every language imaginable, and Helen Magnus was one. That was Helen's reserved way of saying, "I'm glad you didn't die today."

He mirrored her, squeezing her hand and smiling at her. His thumb stroked the back of her hand. After all, he wasn't the only one who'd had a close call today.

His smile dipped into a smirk, considering various ways they could express these particular thoughts when they got back to a nice, soft bed… Or perhaps before.

A rather wicked gleam came into her eyes, her grip on his hand tightening.

"Oh," Nikola muttered out loud, swallowing. He was about to suggest they get up and start back immediately, but he was preempted by a cracking noise coming from the jungle surrounding them, a sound close to his ear like the whine of an insect, and a loud thump in the mud right next to his head.

Like lightning, Helen shot up, dragging him with her and throwing them behind a large fallen tree trunk as more bullets pierced the air around them.

"The Serpent Brotherhood," she hissed after they were under cover, though not the sort Nikola had had in mind a few short moments ago. "They must have tracked us."

Nikola was feeling even less friendly to evil cabals than usual at the moment. "Oh come on. It never ends," he grumbled, daring a peek out above the tree before Helen pulled him back down.

"Don't get me wrong, I mean, I wouldn't have it any other way," he said, and, perhaps strangely, he meant it. "But couldn't they have waited a few minutes?"

Helen just gave him a look, but as she leaned up to return fire, he thought she smiled.