The evening shadows lengthened as Gaius stirred a pot and tried to keep his eyes open.

Camelot had been struck by a nasty outbreak of catarrh over two weeks earlier, the worst it had seen in many years. Prince Arthur released Merlin from his duties so he could help Gaius exclusively once the full extent of the epidemic became clear, but both of them had worked all day and long into the night ever since.

There had been no deaths, but a great many people, from the Lower Town's children to the knights, had been very ill, and Gaius suspected that Lady Agatha's baby had survived only by the aid of magic. Merlin's healing wasn't strong, nor was it terribly reliable, but Gaius knew perfectly well that his vapor treatment had failed. There was no other explanation other than magic for why the blue-tinged child without enough wind even to cry properly suddenly turned pink again and began to wail forcefully just moments after Merlin picked her up.

Then, of course, the prince had fallen ill himself, and looking after him was added back on to Merlin's list of duties. Arthur was only now on the mend after five days of fever. Fortunately, King Uther had escaped the catarrh; in his current state, Gaius feared that he lacked the strength to fight it off.

As he bent to stoke the flames beneath the pot, Merlin slipped in, sagging with exhaustion.

"Why don't you fix us some dinner while I finish reducing this tonic? There should be beans soaking next to the fire."

"Dinner. Right." Merlin rubbed his face with both hands.

A hint of … something in his ward's voice made Gaius look up at him hard. Perhaps Merlin wasn't just tired out. "Come here." Still stirring with his left hand, he grabbed Merlin's chin with his right, checking his pulse, palpating under his chin, then feeling his forehead and the back of his neck.

"You've got it, haven't you?"

Merlin looked startled by the idea. "I have?"

"Yes, you do."

"Oh." Merlin dropped into a chair.

"No, don't sit down here. Bottle on the end of the table, pour out a finger's breadth for yourself and drink it down."

Merlin obeyed. Gaius tilted his pot, examining the tonic carefully. "Up to bed with you, now, and don't fall asleep with your boots on."

It was less than a quarter hour before Gaius finished his brewing and climbed the stairs to check on Merlin, but the young man was already deeply asleep. He was sprawled across the bed still mostly dressed, but he'd managed to remove boots and trousers, so Gaius just pulled the blankets over him and let him lie, leaving the door open so he'd hear if Merlin called out in the night.

Merlin slept like the dead, clear through until morning, fever combining with deep exhaustion to drag him under, but eventually the pressure in his throat and chest woke him, and he began to cough loudly.

Gaius was there almost at once, it seemed, giving him water. For a wonder, the water actually stopped him coughing for the moment.

"I told you not to catch it." Gaius scolded, sorting through the bottles in his kit.

"Sorry, I tried not to." Merlin turned his head to the side, embarrassed.

"Under the circumstances, I suppose it was unavoidable. Matter of fact, it's remarkable that you held out this long."

"You didn't get sick."

"One of the advantages of being my age is that you've had just about everything already." Gaius finished fussing with his potion bottles and handed one over to Merlin.

The ingredients were quite familiar to Merlin, as he'd prepared several batches these past weeks, but this was the first time he'd actually tasted the finished product. Mallow, licorice, and a touch of honey made it taste far better than most of what Gaius brewed, but the willow and a few other things gave it a bitter undertaste. There was just enough wine in the potion to warm his ears without setting off his stomach. Merlin's eyelids drifted shut as he put the bottle down beside his bed.

"I don't suppose you want any porridge," Gaius asked softly, hand still on Merlin's chest. A vague disgusted noise answered him. "Well, here's a fresh cup of water, in any case. It'd better be gone when I get back. If I can't get back at midday, I'll make sure someone checks on you and brings up some hot broth."

Merlin's eyes opened again. "Gaius. I'll be fine. You're needed in town, now go."

"I'm sure you're right." The elderly man sighed and stood up, but he stood in the doorway a moment more, watching until Merlin's slightly congested breathing evened out into the rhythms of true sleep.

The sun was high overhead when Merlin's eyes snapped open again. Someone was using magic in Camelot, quite a bit of it, and it felt like trouble. He sat up slowly, groaning as his joints protested. Outside the blankets, he shivered violently. Abandoning dignity in favor of warmth, he wrapped the blanket around himself. His questing fingers found a pair of trousers and slipped them on, but when he bent down to put on his boots, his head pounded and his vision went red. Fine, he'd just make do without boots then. Dash out, track down the trouble, back to bed before anyone knew he was gone. Assuming Merlin could get down the stairs without falling, of course.

Descending the stairs backwards was probably safest, he decided. He kept one hand on the wall and felt out each step carefully with his toes.

The sense of sorcery hadn't faded when Merlin finally picked his way down the last step and stumbled out into the corridor. The guard on duty looked him up and down, half-dressed, wrapped in a blanket and wavering on his feet, hair no doubt sticking up in every direction, but he didn't try to stop the young servant. Perhaps Merlin should have taken the time to make himself a bit more presentable? No, that wasn't necessary. The faster he got this over with, the faster he could get back to his room, maybe even in time for the promised hot broth.

Absolutely everybody else got a rest when they caught this. But not me, I have to run off and save Camelot again. Why does it always, always have to be me? Keeping a hand on the wall for balance, he set off down the corridor.

Arthur Pendragon, once and future King of Camelot, was in a vile mood. Bad enough he'd been confined to bed for the past five days, and Gaius had forbidden him to train under arms for at least another week. Worse that merely dressing still left him winded, suggesting Gaius might actually be right.

He'd finally managed to leave his chamber and get to the council hall, only to find that most of the younger knights were either down with catarrh themselves or recently recovered, while certain knights of his father's generation, the ones he trusted least, had escaped the fever. Uncle Agravaine, fortunately, had remained perfectly healthy as well. Thank heaven someone had been able to an eye on things. Though this fever hadn't proved terribly dangerous, the normal business of Camelot was entirely interrupted. And worst of all, Camelot had been attacked by something his sword couldn't defend it against.

Of course, just to add to the prince's general frustration, Merlin had managed to wait until nearly everyone else was well to come down with it himself, meaning he'd be useless for a good while yet. More useless than usual. Matter of fact, Merlin had looked absolutely trashed when Arthur sent him off the night before. Arthur was fairly sure Merlin would be fine, though. Definitely fairly sure.

Just then, the prince's irritated musing were interrupted by someone coughing. Merlin was not in his bed, but standing in the corridor in front of Arthur and his knights, apparently trying to hide behind a pillar. His efforts at concealment were clearly doomed, as he was coughing loudly enough to wake the dead. He had a blanket wrapped around his shoulders, his usual scarf was missing, and his trousers were inside-out, seams protruding noticeably. Oddest of all, his feet were unshod, thick and much-darned socks covering his knobby feet, and he held a boot in one hand, clutched like a weapon.

Merlin turned to look at him, eyes glazed with fever but still trying to focus. He took a careful breath, managed to stop coughing. "There's an invader," he rasped. "Wait here, I'll stop them."

"You? What are you going to do?"

"I'll… I'll trip them when they come past me."

"So, there are enemies inside the castle, which somehow you've managed to detect even though they're hidden from everyone else, and you're going to stop them with… a ratty blanket and one boot."

Merlin looked at the boot as if wondering how it had gotten into his hand, then shrugged and looked back at Arthur. "Exactly," Merlin replied cheerfully. Then he started to cough again.

"Have you truly lost your mind, or are you just delirious? Go back to bed. The invaders be gone when you wake up, I promise." Sarcasm dripped from Arthur's voice.

Merlin just stared the prince.

"No, wait, I can't let you wander around alone in this state." Arthur shook his head and looked behind him. "Ah, Gwaine! Can you get this idiot back to bed before he hurts himself?" With that, he stalked off.

Gwaine grabbed Merlin by a fold of his blanket and began leading him back to his little tower room. As soon as Arthur and his entourage were out of sight, however, Merlin planted his feet stubbornly.

"I can't go back to bed. Camelot really is in danger."

The knight turned and placed both hands on Merlin's shoulders, looking at him hard. Merlin met his gaze evenly.

"Who am I?"

"Sir Gwaine."

"Where are we?"

"Corridor, near the Council Chamber."

"And what year is it?"

"The twenty-ninth of Uther's reign."

"You're sure about this invader?"

Merlin nodded. "I swear, there's trouble. I don't know what kind yet."

"Well, you might be wrong, but you aren't raving. Good enough for me. What now?"

"When I last, um, heard them, it sounded like they were heading towards the armory."

Gwaine nodded. "You are aware that your trousers are inside out?"

A hint of color crept onto Merlin's cheeks, but he held his tongue, turning to march down the corridor again.

A moment later, Merlin stopped them. "Not the armory. It was the wrong corridor for that. The Great Hall." He paused, then doubled over to cough until he was breathless.

Gwaine pulled out a flask and offered it to him. Merlin took it gratefully, feeling the warm burn of mead ease his throat.

"You know, mate, I caught this almost two weeks ago and I still don't feel quite right. Are you sure you don't want to let someone else handle this?"

"No, I've got it." Merlin drew in a breath, carefully, and the pair turned around and marched in the other direction.

Merlin stepped carefully down the hallway. Gwaine kept a hand on his elbow. It was discreet and friendly, but it was also a welcome aid to his balance.

They opened the Great Hall doors quietly and peered inside. The Hall had stood empty since the fever first broke out, as there were few opportunities for feasting with everyone either ill or busy tending the sick, and Gaius had recommended a ban on large gatherings until the epidemic subsided. All of this meant that the strange man bending over into the huge fireplace had no business being there.

"Is that him?" Gwaine asked under his breath. Merlin nodded, and the two moved forward, Gwaine leading, keeping his sword arm in front of Merlin. But before they could reach the man, Gwaine flew backwards.

Merlin stepped up and faced the man. The sorcerer tried to throw him across the room as well, but Merlin countered. It was surprisingly difficult, either this man was very strong, or Merlin's fever was interfering with his magic. He threw force at the other man, but it had no effect. The man picked up a bench with his mind and flung it at Merlin. Merlin flung it back, but the stranger deflected it, twisting his wrist to the side. The bench crashed to the ground behind him.

The man was casting with only one hand, Merlin realized. The other held some sort of object in front of his eyes. Perhaps it was a magical object. There were items that could drastically increase a sorcerer's power, turning a minor talent into a truly dangerous one. If the enemy was relying on a focus object, that opened up an entirely different avenue of attack.

Instead of throwing his power at the other sorcerer, Merlin flung it at the object. It was indeed a powerful focus object, but if Merlin could rip it from his hands, the enemy would be helpless. The other man, realizing his plan, focused his own power on grasping the object tightly. Both strained, pulling it in two directions. Spots swam in front of Merlin's eyes, but he held on tightly. The sorcerer, however, realized he had begun to weaken. Behind Merlin, another bench rose silently and swung through the air toward his back.

What neither of them realized was that the focus object was only enchanted clay, and it had been pushed too far. Abruptly it burst, shards flying in every direction, slicing at its wielder's face like glass. The stranger's magic collapsed all at once, the bench crashed to the ground, and the sorcerer fell to the floor.

When the spell shattered, it overwhelmed Merlin's magic senses, seeming loud enough to burst his ears. The sorcerer was defeated, but Merlin just stood there, wobbling. "I did it," he announced to the silent hall.

He should probably check on Gwaine, Merlin though, but his limbs were growing heavier by the moment. Perhaps he'd just take a short nap first.

Though Merlin did not realize it, the spell had shattered audibly, with a sound so loud most of the citadel heard it, including Arthur and several knights sharing an informal lunch in a smaller chamber nearby.

"That was the Great Hall!" Leon shouted, and the group rose and rushed toward the hall. They opened the doors and stared inside at three men, none of them moving.

Sir Gwaine slumped against the far wall as if thrown there, his sword yards away. Nearest to the door, a stranger lay facedown on the ground, a small pool of blood under his head, arms spread out to the sides. And just beyond the stranger was Merlin, simply curled up in his trusty blanket as if he'd decided the near-empty hall was as good a place as any to get some sleep.

Arthur stepped forward as knights rushed to check their fallen friends. "Sound the alarm and start a search, there may be other intruders. Place this man under guard, but don't harm him until we know what happened."

The prince paused. "How are they?"

"This fellow's alive," one knight announced. "Looks like he's just bleeding from some cuts on his face."

"Merlin also."

Gwaine stirred, raised a hand to his head. "What was that?

"We were hoping you could tell us," Leon replied, heading over to him.

Sir Gwaine looked around. "Merlin insisted that there really was an invader, so I followed him here. A man was doing something to the fireplace."

"This man?" Arthur asked, pointing at the the stranger.

"Yes! But when we got close to him… I think he used sorcery on me. Threw me across the room. That's all I remember."

"Perhaps Merlin took him out with that boot," one of the knights suggested. The group laughed softly.

"Maybe Merlin did manage to knock the sorcerer down, while he was occupied with me," Gwaine answered matter-of-factly. "I know there wasn't anyone else."

Just then, Gaius hurried in. "What on earth happened here?" Not waiting for an answer, he rushed toward Merlin, still lying on the floor. "He's gone cold, like a man in shock. It's not the fever, there's something else at work here, but I don't see any wound." He shook his head. "I need someone to carry him back to his bed."

A large crowd had gathered around the doors of the hall. One of the servants at the back of the crowd stepped forward and simply picked up Merlin, blanket and all. Two guards picked up the still unconscious intruder and began carrying him off to the dungeons, and Leon bent to help Gwaine up. As the guards carrying the stranger walked past Gaius, he stopped them.

"There's something around this man's neck, some kind of token." The physician lifted it carefully by its cord. "Serpent-shaped, I believe this was an amulet of dark magic. But it's broken now, it should be harmless. I'll just make sure it's properly disposed of." He grabbed a cloth out of his pocket and stowed it away, amulet wrapped inside.

By the time Gaius returned to his workshop, several people lurked outside the door, some clearly anxious, some, such as Arthur, trying to appear nonchalant. "They took him upstairs," Gwen announced.

"It'll take me some time to examine him, so you might as well get back to work. I'll send word as soon as I know how he is."

Merlin was already there, neatly laid out in his own bed. Lancelot was standing beside him.

Gaius stared at him. "I distinctly remember telling you that you were not to get up until tomorrow."

Lancelot shrugged. He held a naked sword in one hand, but wore no armor. In fact, he seemed to be wearing only a red cloak and a bedgown. "The alarm bells made it somewhat difficult to rest."

"Well, as long as you're here, you might as well stay. I could use another pair of hands. The first thing is to get him warm."

Merlin was still cool to the touch and alarmingly still, skin so pale it was nearly transparent. The two wrapped him in blankets with hot stones. Once the heat began to soak in, however, Merlin shivered violently. "That's a good sign. Means his body is trying to warm itself. Now, one of those gawkers was kind enough to bring some broth, so let's see if he can be roused enough to drink."

"Gaius, what's wrong with him, really? Is it something to do with magic?"

"I'm afraid so. Lift his shoulders for me? Yes, thank you." He spooned the broth into Merlin's mouth. "Good lad, swallow it down. A bit more now." Slowly the cup of broth disappeared into Merlin's mouth.

"It's not a curse or poison," Gaius went on, "It's just the exhaustion of too much casting, which is not good in someone already ill. Speaking of which, you'd best get back to your own bed, don't need your fever coming back."

Merlin was still pale, but his skin was warmer and he was breathing more deeply. Lancelot turned to go as ordered.

"May I return tomorrow?"

"Yes, please do. Eventually I'll have to check the other patients, and I don't want Merlin left alone. If I can't look after him myself, I'd rather it be one of Merlin's friends."

"I would be honored to care for him." Lancelot replied.

By the time Lancelot returned the next morning, Gaius's fears were confirmed. It took hours for Merlin to stop shivering, and when he finally did, Merlin's fever was much higher than it had been before. His eyes had opened a few times, but he never roused fully. He'd muttered a few words, but nothing that made any sense.

The room seemed to waver like a valley glimpsed through fog. Merlin's feet at the end of the bed looked a terrifying distance away, as if he'd grown twenty feet tall. Then the cupboard moved in closer, until Merlin was sure it would fall on him, spilling out snakes and spiders onto his face. Then, with a pop, the fever dream would pass and the room would return to its normal shape. The blankets rubbed at his skin like sandpaper. He was made to drink things, some of them vile, some tasting rather nice, until he drifted in a half doze, close to comfortable.

For some reason, Arthur had dragged him out to the practice yard at night, and now he was sitting on Merlin's chest, armor and all. It was dark, so he couldn't see what was happening, but that was the only possible reason why it was so hard to breathe. Merlin sucked in air as hard as he could, but it only made him start to cough, a rasping, painful cough. He wanted to tell Arthur to get up, but he couldn't stop coughing long enough to talk, and when he reached for his magic, it just slipped through his fingers.

Then Gaius was there, yanking him out of half sleep and forcing him to sit up. There was a strong scent of mint and steam in the air. "The fever is trying to settle in your lungs, boy. We must not let it do that." Merlin had seen that several times in the past weeks, mostly in babies and little children, the fever moving deep into the lungs until they struggled to breathe. Distantly, he wondered if his lips were blue, like Lady Agatha's baby. He wondered if blue lips would look strange on him.

The nice potions stopped, and there were only the nasty ones. He slept less after that, too, and coughed more. Every time he woke, someone was sitting beside him, Lancelot, Gaius, one of his friends among the servants. Sometimes Gwen came, too, but never when Lancelot was there. Or else he wouldn't come when she was there, Merlin couldn't figure it which it was, and somehow it seemed terribly important.

Finally, the bands around his chest loosened and he woke clearheaded. This time, Gaius was the one by his side.

"Had the oddest dream," Merlin mumbled. "There was this sorcerer creeping around the castle." He laughed briefly, before it turned into a coughing fit. Gaius wasn't laughing at all.

"There was. Somehow, you found him and destroyed the amulet he was using."

Merlin blinked. "I think I remember… was Gwaine there?"

"Yes. But Merlin, destroying the amulet nearly killed you. Your magic takes strength, and you were already quite ill. Running around the castle barefoot for hours and then attempting some sort of sorcerers' duel was the last thing you needed. Promise me you won't be so reckless again."

"I didn't exactly have a choice, Gaius."

"Well," Gaius paused. "Next time wear boots."