Merlin spends three days and nights on the shores of Avalon, unable to leave the closest thing he has to his king's side. He tries amidst the grief to find a spark of happiness in knowing that Arthur had finally truly known him before passing beyond the reach of mortal men, but he fails.
On the second day, he conjures a bird and sends a message to Gaius. The king is dead. Long live the queen. Guinevere will be a good queen--has been a good queen--and will lead the people with kindness and justice, but that is a cold comfort.
On the third day, he stares at his rippled reflection in the lake and ages himself from young to old and back again, wondering what Arthur would have looked like in his dotage had Merlin not failed. He cries, sharp with longing and pain and need, his magic churning within him and leaking from the bounds of his body, dripping from his fingers, his elbows, his nose, as if it is crying, too. It swirls into the lake, disappearing beneath the surface.
He is still weeping openly when the boat drifts back. He can barely see it through his tears, alerted only by the lapping of the water that something has changed.
When he wipes his eyes and sees what is before him he nearly destroys it in a fit of unleashed fury before he realizes it is not empty; the eyes of its cargo open as the bow of the boat furrows into the pebbled shore.
"Arthur?" he says, his voice hoarse with disuse, hardly more than a raspy croak.
It is Arthur, but it isn't. The Arthur he sent across the waters of Avalon was dressed as a knight, a king, a soldier. This Arthur is wearing a simple linen tunic and breeches, the bloodstained chainmail he'd lived his last days in nowhere in sight. He has no cloak, no boots. This Arthur does not look as if he has left the mortal world behind, but he does look as if he is no longer wholly a part of it.
"Arthur?" he says again, clearer, and abruptly wonders if he has died, too, and Arthur is here to take him away somewhere where Merlin can remain at his king's side, always. He reaches out toward the boat but freezes with his arm half-extended, terrified that it will vanish at his touch.
Arthur sits up and Merlin jerks back, scrubbing at his eyes with the cuff of his jacket. The boat rocks as Arthur swings one bare foot over the side. The world does not end as Arthur disembarks, pebbles shifting under his feet as he takes the few steps to Merlin and drops to his knees.
"I am made anew," Arthur says stiffly, formally, as though the words are not his own.
Hearing Arthur's voice, seeing him speak--something breaks inside Merlin and he has to know, he has to know now and he half-scrambles, half-falls forward as he rises to his knees and throws his arms around Arthur's shoulders. Arthur catches him, and it is everything he's ever wanted, will ever want.
Through his tears, he says, "I didn't think being the Once and Future King meant you only took a three day break."
Arthur's hands come up to cup Merlin's elbows, pushing gently. For an instant Merlin is scared that once he lets go Arthur will disappear for good, but Arthur does not break the contact between them, his touch sliding up Merlin's arms to his wrists.
"Not?" Merlin repeats dumbly. His fingers find Arthur's face, cupping his jaw and rubbing his thumbs over his cheeks, memorizing the feel of warm flesh.
"King. Not right now. Not for a long while."
Arthur lets go of one of his wrists to press gentle fingertips to Merlin's lips, stilling his protests. "Camelot is made. Albion is made. It has a strong and kind queen to guide it."
"I don't understand," Merlin says, helpless. He does not move away.
"They said--" Arthur seems unsure, as if he can no longer remember of whom he speaks. "They said this was our reward. This time together--until I am needed as a king again."
"Arthur," Merlin whispers, eyes sliding closed as the last of his tears escape only to be brushed away by his king, his Arthur.
"Merlin," Arthur replies, voice gaining strength and certainty. Their lips touch and Merlin can't help the smile that spreads over his even as Arthur pulls him closer, deepening the kiss and making him whole, whole again.