A/N: Thank you GuestM, Buckhunter, SnidgetHex, and PadrePedro for reviewing the last episode! Actually, Lancelot and Gwen are in an established relationship. This AU seemed like a good place to give them that. ^_^


Chapter 1

Gaius knelt on the grass in the glade, checking on the health of the baby unicorn while Merlin held the foal still. Gaius measured its heart rate, weight, and overall appearance.

"It's doing very well," he concluded.

Merlin smiled and released the baby, who went darting away. "Good," he said, but then his expression fell. "I don't know whether to try releasing it back into the Forests of Gedref or not. It's alone here, but finding its kind is difficult, as they're so rare already."

"It's safe here," Gaius pointed out. "And it seems happy."

They both looked over at the pool as the Vilia rose up from the water and began to bob around the unicorn, which pranced about in delight with the floating lights.

They got to their feet then, Gaius grimacing at his creaky knees. There were times he envied Merlin his immortality. He spotted Percival making his way toward them.

"The messenger falcon from Camelot brought a letter for you, Gaius," the man said and held out a rolled up piece of small parchment.

Gaius took it and unrolled the top, instantly recognizing the handwriting of his friend Alice. They'd known each other in their youth, had even been engaged, once upon a time. But then the Great Purge began and entire communities had been ripped apart by suspicion and fear. Plus, Gaius had taken a young warlock under his wing, and it just wasn't safe for them to stay, so he'd left. They'd reconnected years later, and Gaius learned she'd been appointed court physician in Camelot. A shared love of healing had been one of the things that'd brought them together in the first place, and they'd corresponded regularly about their various new discoveries. Gaius was eager to read the letter. A part of him still loved Alice, even though it wasn't tenable for the two of them to be together.

Merlin gave him a knowing smile. "We'll leave you to it," he said and started to leave with Percival.

Gaius couldn't suppress his own smile as he unrolled the parchment the rest of the way and began to read. But after the first couple sentences, he stopped and called, "Merlin!"

The warlock turned with a questioning look.

Gaius moved to catch up with him. "There's a plague sweeping through Camelot, something Alice has never seen before." Now that he had Merlin's attention, he quickly turned back to read the rest of the letter. "She thinks it's sorcery," he went on.

"I am out of my depth here, Gaius. Please, I am asking for your help."

Gaius looked up. "I must go. But if Alice is right and it is sorcery, I could use your help."

Merlin nodded. "Alright."

Gaius smiled gratefully.

Unfortunately, when they went to inform the others of their errand, they were not onboard at all.

"You're recognizable," Elyan pointed out to Merlin. "You'll be arrested on sight, or worse."

"Arthur didn't tell Uther about me," Merlin responded.

Gwaine scoffed derisively. "Maybe not about the griffin, but after your magic display with the unicorn? It's too dangerous."

"I'll be fine," Merlin insisted.

Gaius pursed his mouth. "Perhaps they're right and it's too dangerous."

"Gaius," Merlin interrupted firmly. "A magical plague is right up our alley; of course I'm not going to sit it out and hide."

Gaius shook his head. "Uther is as vindictive and cruel as his father was."

"And he doesn't know about me."

"You can't gamble your life on that princess!" Gwaine exclaimed.

Merlin rolled his eyes. "Honestly, sometimes I think you all forget I'm much older than you. I've survived this long; I'm not going to stop now."

With that, Merlin turned and marched off to gather supplies for the journey, effectively ending the discussion. Gaius was torn; he still felt protective of Merlin, despite the warlock's age and power, and yet also valued his help, and he couldn't deny Alice's request for assistance.

So he pushed his doubts aside and went to his hut to pack his own medicinal supplies, specifically a variety of magical remedies that could work on curses. Then he and Merlin set off toward Camelot.

It had been years since Gaius had visited the great city, but it looked just as it always had. He figured he remembered the way to the court physician's chambers, but still politely asked some guards for directions. He and Merlin made their way through the corridors until they found a plaque outside Alice's door. Gaius knocked to announce themselves but opened the door without waiting for a response.

"Hello?" he called, poking his head inside. A small smile lifted the corners of his mouth as he found a work space not all that different from his back at the Sanctuary—shelves full of books and jars and vials, a cauldron bubbling over the hearth. And Alice was sitting at a work table, rolling up fresh linen into bandage rolls.

She looked up at their entrance and broke into a wide smile. "Gaius!" she exclaimed, getting to her feet and hurrying over.

"Alice," he returned, the two of them embracing. "Why, you are just as beautiful as I remember."

She scoffed and gave his arm a light slap. "Your eyes need spectacles."

He grinned. He wasn't only being flirtatious; he did find himself quite taken by the sight of her.

"And who is this young man?" Alice asked.

"This is Merlin," Gaius introduced, "my apprentice. And while I would love to sit down and catch up, this illness sounded very serious, so I think we should see some sick patients."

Alice nodded soberly. "Of course. Come with me."

She took them back out of the castle and into the lower town. They visited three houses that held ill people stricken with fever and chills. But they lacked any of the other symptoms typically associated with a normal illness.

Gaius waited until they stepped outside before asking quietly, "What exactly makes you think it's sorcery?"

Alice's mouth was set in a grim line as she led them to a building on the very edge of the town. "The dead are being gathered here," she explained.

Gaius stepped inside, only to pull up short at the sight that greeted him. Of course, he had seen his fair share of sickness and the dead that sometimes accompanied an outbreak, but he had never seen anything like this before. The corpses were icy pale, eyes milky white, with the veins beneath the skin standing out a stark blue.

Merlin came up next to Gaius to get a look for himself, and Gaius arched a subtle brow at him. The warlock nodded in confirmation of their suspicion.

"You are correct," Gaius said, turning back to Alice. "This is not a natural illness."

Alice did not look encouraged by the affirmation. "I don't know how to stop it," she said, distressed. "None of my treatments have worked. It's not even contained. Members of the court are falling ill as well."

Gaius pursed his mouth thoughtfully at that. "I don't imagine members of the court mingle with the people of the lower town, therefore it must not be spread through physical contact."

Alice nodded her agreement. "Another clue that this is sorcery, but then how to trace it if it strikes randomly?"

"Even sorcery follows rules," Gaius replied. He roved his gaze around in contemplation, mentally reviewing everything he knew about both subjects. He spotted a woman filling a bucket at the well. "Alice," he said, straightening with an idea and heading toward the well.

Alice and Merlin followed. Gaius peered into the well, then at the pump that was to refill it when it got low.

"The entire city gets its water from one source, does it not?" Gaius asked.

Alice's eyes widened. "Yes. There is a well up at the castle, but they both come from the same underground source. You think the water is contaminated?"

"It's a good place to start looking."

They hurried back to the castle, which had tunnels that would take them down to the water source. But before they could reach them, they were stopped by a pair of guards.

"The king has summoned you and your friends, Alice."

Gaius stiffened and shot a concerned look at Merlin, who managed to maintain an unperturbed mien as the guards took them to the council chambers where Uther was waiting. The king looked peeved as he addressed Alice, hands on his hips.

"Who is this?" he demanded, indicating Gaius.

"This is Gaius," Alice replied. "He is a colleague I contacted for help with this plague."

"You are incapable of handling the matter yourself?"

"A wise person seeks counsel for matters of great importance," she replied staunchly. Pausing, she then added cautiously, "And this disease is not natural. It is sorcery."

Uther's eyes widened in fright at that, and murmurs went through the nobles.

"My lord, we have just discovered that the water is the likely source of transmission and were just on our way down to the tunnels to investigate further," she went on.

Uther nodded, his irritation at unannounced strangers in his kingdom momentarily forgotten. Until he narrowed his eyes on Merlin. "I recognize you. You were with the hunters who came to slay the griffin. And now you are with this…traveling physician?" he asked, eyes sharp and suspicious.

"Gaius is my regular master," Merlin replied. "But sometimes he loans me out as a guide in Camelot for extra coin."

"You know those hunters slipped away with my prize griffin," Uther said.

"Er, yes, I'm sorry for that. They can be…independent."

Uther huffed and finally waved them off. "Find the cause of this plague," he instructed sharply.

The unspoken warning of if they failed was clear.


The three of them left the chamber, but the next thing Merlin knew, someone had grabbed his arm and was pulling him aside in the corridor.

"What are you playing at here?" Prince Arthur hissed.

"Nothing," Merlin responded. "Gaius is a physician. The only game is that he works for me and not the other way around."

"Why do you keep going around pretending to be a servant?" Arthur demanded.

"I can't very well admit what I really am, now can I?" he retorted. "And what does it matter? We're here to help, and right now you've got a magical problem, which is the kind of thing me and my friends handle."

"Your kind are the ones who make these problems," Arthur snapped.

Merlin just shook his head. "If you truly think I'm evil, why haven't you told your father who I am?"

"I should," Arthur rejoined, but then hesitated. After a moment, he shook his head grudgingly and released Merlin. "You really think there's something in the water source?"

"There's something somewhere."

Arthur heaved an audible exhalation. "Fine. I'll take you down there."

Merlin didn't say anything as they went to catch up with Gaius and Alice, who had stopped a ways ahead but not doubled back to interrupt them. Neither of them commented on the fact that the prince was taking them down to the tunnels beneath the castle vaults.

"The well is this way," Arthur said, holding a torch and taking the lead.

They came upon three large wells of water next to each other. Merlin and Gaius stepped up toward the edge to inspect the water, but something rippled beneath the surface, and Merlin yanked Gaius backward just before a hideous monster came surging up with a splash. Alice screamed, and Arthur drew his sword, brandishing both it and his torch at the creature. It roared and slapped the torch out of his hand. Arthur swung his blade.

Merlin scrabbled to snatch up the fallen torch and swiped it at the beast as well, letting his magic rise to the surface in a subtle show of force. The creature roared in outrage and turned to dive back into the water.

Arthur hesitated for a moment before turning to usher everyone back down the tunnel toward the exit.

"Well, now we know for sure something magical is poisoning the water," Merlin said.

"What the hell was that?" Arthur exclaimed.

"An Afnac," he said, sharing a grim look with Gaius. "And it didn't end up here by accident—it was conjured."