SPOILERS FOR: "The Darkest Hour (Part 1)" and the clip from "The Darkest Hour (Part 2)".

"Take me with you, you don't understand, please, Arthur, I have to go with you."

There is a moment, when Arthur stands back and watches Lancelot lead Merlin back to Camelot, that makes a very strange but very, very heavy weight settle in the pit of Arthur's stomach. It's something like fear, he thinks, but fear is an acute feeling, something sharp in your chest. But this is bigger, and it reminds Arthur of when he was very small and his father took him to the highest tower of the palace late at night to show him the stars. And Arthur had stared at that vast expanse of night sky, and he knew what he was looking at, knew what the sky and the stars were, and he had smiled in amazement and said, "The sky is very big, Father!"

And Uther had nodded, and like a good parent he had asked a perfectly pointless question, "How big is the sky, Arthur?"

And for some reason that made Arthur frown, and he thought about it, and carefully said, "Perhaps…as big as the ocean," but immediately disagreed with himself and said, "Well, no, 'cause the ocean's got shores, hasn't it? Beaches happen where the sea ends."

"So how big is the sky, Arthur?" Uther had asked again, this time with a chuckle, and at the time Arthur didn't find anything very funny at all about it because the night sky was indeed very big, but there certainly wasn't an end to it that Arthur could see.

"It's bigger than everything," Arthur had said. "Does the sky stop?"

"The sky doesn't stop."

"If the sky doesn't stop but the world stops, then the sky is bigger than the whole world," Arthur had said, clutching at Uther's hand as he stared out at the stars. They had twinkled in a cold sort of way that Arthur no longer liked very much.

"The sky is so big that no one's found the end 'cause there isn't an end," Arthur had concluded, and Uther had agreed. He was surprised when Arthur said he didn't want to look at the stars anymore, but he took him back inside, and for a few minutes Arthur had been quiet, dealing with his first existential crisis, until Uther had asked him what was wrong and Arthur said, "I don't like not knowing how big the sky really is," and Uther had fixed everything by saying, "All right. Let's try an easier question. How much do I love you, Arthur?" and Arthur had flung his arms wide and answered, "This much," which was correct and the size of the sky was forgotten.

This moment, Arthur thinks, is sort of like the question of the sky. But bigger. The way Merlin stared at him from his slumped position on the horse. Cold and grey, eyes rimmed in red, and yet he strained to speak, only to plead with Arthur not to send him back.

"I have to go with you," had made Arthur only say his name, gently forbidding any further discussion, but now he wants to know why. Why does Merlin need to go with him? Why does Merlin go anywhere with him? Arthur brings him everywhere for stupid reasons and when he doesn't, Merlin comes anyway, with some stupid reason of his own, usually something that has to do with protecting Arthur.

It used to be funny, the idea of Merlin protecting him, the idea of Merlin saving his life. They'd discussed it when Arthur had been shivering in his armor, laughing about it. "You don't know how many times I've saved your life," and it was funny because Arthur could count on one hand the times Merlin has saved him, but not two minutes later he saved him, threw himself into the wintry screams without batting an eyelash simply because he'd seen that Arthur planned on doing it himself. He did it without hesitation, without a look back, like he'd done it a thousand times before. "You don't know how many times I've saved your life."

How many times have I saved your life, sire?

Arthur doesn't know how big the sky is and he doesn't know the answer to this question either. He thinks about the times he's been knocked unconscious in the middle of great battles and woken up to Merlin hovering over him, the battle finished. And Merlin would congratulate him on whatever he'd done, "you've saved us all," and all that and of course Arthur believed him because he's Arthur and saving people sounds like him, not Merlin.

How big is the sky, Arthur?

The sky is so big that no one's found the end 'cause there isn't an end.

How many times have I saved your life, sire?

More times than you've cared to let on, Arthur answers the imaginary Merlin in his head. Arthur is rather disturbed by this, even more so after looking at Merlin's corpselike face, lips barely moving as he begs Arthur to take him with him.

How many times have I saved your life, sire?

I don't know, but obviously you were planning on doing it again, Arthur thinks. Merlin was aware of Arthur's plan to sacrifice himself at the Isle of the Blessed.

"No man is worth your tears," Arthur had once told him. He wishes he had added, "And if there's any man less worthy of your blood, it's me."

How big is the sky, Arthur?

The sky is so big that no one's found the end 'cause there isn't an end.

How many times have I saved your life, sire?

I don't know, but obviously you were planning on doing it again.

How much do I love you, Arthur?

Arthur doesn't know who's asking the question this time and he still doesn't know how big the sky is, sort of for the same reason.