Arthur wasn't exactly surprised. Merlin had seemed a bit...jolly. Even for Merlin. Perhaps his manservant should muck out horse stalls the next time there was a feast; if the boy collapsed at every major festival of the year, people would start to talk. More.

At least this time Merlin staggered a bit but didn't fall, avoiding the attention of the etiquette-conscious nobility. The only eyes his clumsiness drew were Gwaine's, the knight tracking him as he stumbled for the servants' corridor. Arthur excused himself casually, not wanting to miss out on the opportunity to berate Merlin for his indulgence. When they were hidden from the view of the court by the massive pillars of the great hall, he steadied Merlin gently.

"Started the revelry a bit early, did we?"

"Arthur."

He'd been about to make another witty (well, the wine made it seem witty) remark about servants who imbibe too freely, but his throat seized as though his voice had been plucked away by a hunting hawk. Merlin's eyes looked very blue and very wide, glittering in the wavering torchlight with a fey shine that the king found difficult to reconcile.

"They're coming. It's tonight."

"You're talking nonsense again, Merlin. Go sleep it off before you set someone's beard on fire." He tried to force an unconcerned imperiousness into the words. Somehow, they carried all the weight of a leaf before a thunderstorm.

"It was all for you, Arthur. Everything I ever did. I hope you know that."

All bravado fled, and he could only frown in sober confusion.

"I'm sorry."

And with that, Merlin was gone.

The baffled king stood there a moment and watched Merlin hurry down the hall and out of sight. It was typical Merlin, of course: get knackered, say something cryptic, show up next morning looking like you rolled out of a haystack. A cheerful haystack.

He turned back to the feast, even started to shake his head and regain his seat at the head of the long table. But he looked at the gathered nobles, the bright light that illuminated the tables and left the walls in shadow. He listened to the waves of laughter rolling out between the clinks of goblets raised in fellowship.

They're coming.

Arthur turned his motion toward the table into a purposeful stride for the door. This garnered a bit more attention, but the varied conversations continued. As long as the wine kept flowing, Arthur's court would be just fine without him. A brisk gesture to one of the guards outside made the armed man fall into step behind him as he swept down several corridors and a colonnade, heading for the outer battlement. The guards on duty there covered their surprise well; if they thought Arthur's sudden appearance strange, it did not color their reports, which were unambiguously mundane.

He turned to look out over the city, scanning the darkened streets for signs that all was not as it should be. For several long moments, he saw only the torches of patrols and the celebratory bonfires in every quarter. The guards were right: everything looked as it should. But he couldn't shake the echo of Merlin's warning, and dread settled in his gut as he recalled other warnings his servant had offered, warnings which Arthur had ignored. He turned to the solider he'd brought with him.

"Find Lord Agravaine."

Before the man's footsteps had even faded, fires exploded in the lower town, licking through streets and across buildings with uncanny ferocity. No natural fire could burn so swift and hot, gnawing at the city like a living thing. It moved with a steady and obvious purpose, cutting off escape from the castle. In its fierce light, dark-armored troops could be seen approaching the walls that enclosed the courtyard. Arthur felt the cold grip of fear on his spine before a lifetime of training clamped down over it and began issuing orders.

They're coming.

Within the span of a few minutes, Arthur had raced from one end of the castle to the other, sending messengers scurrying in every direction as he went. Orders rippled down the chain of command like grains of sand in an hourglass, stirring the castle's defenses from slumber. To a man, his knights and servants responded with speed and courage, but he already knew it wasn't going to be enough. The enemy was already inside the walls. They might keep the citadel, but the people were in the town.

Arthur's despair grew with every order he gave, because he knew that he had already lost. He had faced heavy odds before, but this...there didn't seem to be any point in it. Except that it was in his blood to fight, as long as he had breath. He simply did not know any other way to react. His heart quailed, but his mouth kept giving orders and his hands reached automatically for the crossbow his servants brought him.

The first catastrophic rumbling swept across the city just as Arthur was turning to descend from the battlements and marshal his knights. The very stones beneath his feet shook like a storm-tossed sea. It was hard not to believe that the citadel would be pulled down on top of their heads. Indeed, several men-at-arms dove to the ground in alarm. Arthur spared a moment to gaze searchingly in the direction of the tumult, but the night hid its source.

"Eyes forward!" he shouted to the cowering soldiers. He didn't pause to make sure his orders were obeyed but leapt down the steps three at a time.

He met Leon in the courtyard, the angry blaze of the burning city casting half of every face in a devilish light. "Sire, what about the lower town? Should we not attempt a defense?"

"The outer walls are lost. We'll be fighting in the streets. I want you and Gwaine with me. Our objective is to cover the retreat of the people into the citadel. Elyon will oversee the reinforcement of the inner wall."

Arthur watched the disbelief and horror flicker across his first knight's face like a shadow across the sun. It was quickly replaced by grim professionalism as he passed his orders on to his cohort. Gwaine and his men rolled in a few breaths later, but they needed no orders. As usual, Gwaine seemed to know Arthur's mind without the necessity of words, as least when it came to a fight. It was one of his most annoying habits.

There was no space for conversation once the battle was joined in earnest. Knights swept through the streets, citizens dashing past as swords rose up to meet the invaders. Archers softened the enemy line where they could, but the risk of hitting Camelot's citizens was high. It was tempting to push forward, but Arthur knew the initial momentum couldn't last. Fresh blades were flooding into the city, outnumbering Camelot's defenders at least two to one. He kept his men in place, ready to fall back once the stream of peasants and tradesmen thinned. The enemy had already cut them off from most of the city, but they could provide refuge for those closest to the citadel.

A second explosion shattered the night, knocking men from their feet even as they fought. Knights and invaders alike began coughing as a thick cloud of dust rolled over the city, blown by an easterly wind. Arthur sliced his way clear of the melee and leaned into that wind, watching as the tide of soldiers ebbed, at least from that flank.

He watched, and he wondered.

"Hold here. Sound the withdrawal when the people are safe."

"Yes, sire." The only sign of Leon's confusion was a furrowed brow. Arthur chose to ignore it, moving off down the streets alone, swiping at invaders as he passed. There were fewer and fewer of them as he moved closer to the source of the fine dust that was settled over this part of the city. In a few minutes, he arrived at what he had known, in the back of his mind, would be his destination all along: the entrance to the one of the recently constructed siege tunnels. It was the only explanation for the invaders' sudden appearance inside the walls of the city.

Arthur squinted in the dim light and tried to breathe as little of the dusty air as possible. It was clear that there would be no more soldiers pouring under the city's walls from here. The tunnel had collapsed, killing the men still passing under and spewing a fountain of debris out onto the tightly patrolled corridor that ran the length of the wall. The hidden steps that had led to the gated tunnel now disappeared under a pile of masonry.

Arthur thought then of the months spent laying out the plans for these tunnels, and the care taken to ensure their secrecy. And he thought of Merlin's insistence that they had been compromised. He saw bright blue eyes in flickering torchlight, and he heard again that whispered warning.

They're coming.

He didn't really think about it. He just ran, down the corridor to the next tunnel, almost losing his feet when a blast swept across the stones like a hundred heavy horse. He wasn't sure if it was relief or dread that welled up in him when he saw Merlin, winding among the bodies of invading soldiers as he made his way to the sharp-cut steps.

Arthur almost called out to him. Part of him believed that if he said Merlin's name, the fool would turn around and explain what was happening, and nothing would change. Instead, he watched silently as Merlin leaned into the tunnel. He watched as his most trusted servant uncovered a bizarre-looking sigil that had been etched into the stones of the tunnel, a sigil that Arthur had never laid eyes on, despite having overseen the construction of the tunnels himself. He heard the strange words that Merlin spoke, and he saw the burnished golden glow right before the tunnel collapsed, as efficiently as any sapper could have devised.

Arthur wasn't really conscious of walking out into the dust-choked alley. He almost didn't notice Merlin's turn at the sound of chain mail and booted feet. But he was aware of the great chasm opening between them, like the world falling away into nothing, and he could only think, not Merlin. Not after everything.

He knew he was supposed to be doing something, but he could only stand there, his bare sword practically scraping the cobbles. Nothing in his entire life had made less sense than this. Perhaps he was going mad. Or perhaps it wasn't Merlin at all but a seeming, such as vengeful sorcerers had been known to cast. Perhaps Merlin was dead already.

Yet the expected hateful sneer didn't come. There was no tirade justifying the betrayal, no litany of Camelot's crimes against magic. That was when he knew it was Merlin: when he looked into his servant's eyes and saw not anger, but only a deep, immeasurable sorrow that gradually turned into resignation. When Merlin spoke, his voice shook with something that was not quite regret.

"Your sword is not Camelot's only defense."

He turned away before Arthur could make any answer, and began sprinting toward the next tunnel. When a small scouting party advanced from the other direction, he did not change course or pace, but simply kept running, as though expecting the invaders to part before him. And, borne on an invisible tempest of magic, they did.

Arthur stood there, staring after him, until he disappeared into the haze.