A/N: This is set post 5x13 and is canon with everything except the modern day clip at the very end.
When they finally find Emrys they are amazed. He is cheerful, amused at their deference, laughing at their stories. He does not ask after Camelot and when one of the younger members accidentally lets the name slip he responds politely that he's never been there but is glad that the Queen had accepted magic after her husband's death.
Slowly she understands. They have limited time in the few days that he escorts them through his woods to the other side but in that time she comes to understand the choice he had made. How, to live without that which made him whole was unbearable, so he forgot. Forgot destiny, forgot a long ago trek from his mother's house to the Castle at Camelot, forgot a prince who would one day be a king… and a friend. Because without those memories life was indeed emptier but he was freer. So though she doesn't agree with his choice she understands why he has made it.
The littlest druid boy in their company cries himself to sleep each night that they camp in the Forest of Emrys. He can feel the depthless grief and the agony, a physical pain, that erupts from somewhere inside the soul and turns the entire person away from the light because without your king how can you stand to watch the sun rise each day because it hurts. The boy can feel it in every tree, every rock, the very air. The entire forest morns what its caretaker does not; taking on the pain of a man left bereft of that which gave him purpose, life, brotherhood so that he might walk free of the burden that otherwise weighed him down and sapped his will to live.
As they cross from old pine and hemlock into stands of maple and birch on the third day, their leader bids them go ahead. He turns to their guide and smiles sorrowfully in response to the man's cheerful goodbye. Taking the warlock's hand in his own he presses a single sheet of paper into the palm. With his other hand he wraps the pale fingers around the simple note and nods in response to the confused frown he receives. He turns away confident that he has done his duty.
Merlin nearly forgets about the small scrap of a note in the proceeding weeks. He tucks it in a pocket and runs – quick as a deer – over the dense carpet of needles that demarks his home. He loses himself in the intrigues of the fish and the romances of the squirrels. He turns himself into his namesake and spends a while in the trees and above them.
Then one day, as he is sitting by a campfire that floats midair so as not to accidentally spark an inferno among the dry needles, his fingers come across a worn scrap of parchment in their exploration of one pocket in his equally worn jacket. Curious he unfolds it and squints to decipher the angular letters.
He is returned. Your destiny awaits you.
And below them in a familiar chicken-scratch:
Merlin, come home.
He cocks his head, confused at their meaning. Then everything is clear and though he can't recall the exact moments of laughter that he used to cherish nor what precise grief had driven him to where he now sits he knows that everything is right again. It's time to go home. To Camelot.
He calls down a scruffy looking owl and ties the parchment to its leg. 'Go' he commands.
On the back of the note is a simple response that reads,
Tell him I'm on my way.