One night he returns to his room and finds Erik there.

"Leave, please," he says. "I'm not going to bother asking how you got through our defenses, we'll figure it out in the morning. But please leave."

"Charles," Erik says, and removes the helmet.

"What--" Charles rubs at his forehead, but doesn't read Erik.

"I can't--I want." Erik says haltingly.

"Don't insult me," Charles says, because he can feel the pity and the guilt without even trying to touch Erik's mind. "Whatever you're about to say, just don't."

"I do want you," Erik says. "I won't--I won't apologize, if you don't want me to, but I can't, Charles, please let me--"

And he thinks at Charles then, as clearly as he ever has, please let me touch you. Charles can feel the want, then, underlying both the guilt and the sheer need to apologize.

"It's not the same," Charles says, and then, to clarify, because he's not sure what's happening in this conversation, "I'm not the same."

"I'd want you even if you were, I don't know, made out of spare parts from a car," Erik says, waving a hand.

Charles snorts. "I'd be made entirely of metal then," he says. "I should think you'd want me then."

Erik smiles at that. "Yes, it is a good thought. But please, Charles. I can't sleep without you, I can't think."

"That bodes ill for your attempt at world domination, doesn't it?" Charles says, but he's smiling.