A/N - Old fic this. Originally written in the summer of 2011, just after First Class came out, it was a response to a kink meme prompt. The request was:

"When Erik discovers how badly Charles was injured on the beach, he spends months searching for a mutant with the power to heal. He finally finds one and convinces him/her to help. Charles agrees, but only becuase he doesn't know that the injury can't be cured, only transferred to someone else, and naturally Erik has volunteered himself."

I never finished it back then, and I'd forgotten all about it until I opened my X-Men fic folder after the new movie and found it. Now I want to finish it. Please let me know what you think, and if it's worth continuing.

Of course, I don't own the X-Men themselves. Just the movies and about 20 years worth of comics.

Transference

"Are you sure you understand what you're agreeing to?"

Erik nodded, arms folded and staring down at the mutant standing before him. He had searched for months to find someone like him, and if his power wasn't exactly what he had hoped for, so be it. Perhaps he even deserved this. After all, what happened had been his fault.

The mutant was just a kid, barely seventeen and looking much younger. He was dark haired, slim to the point of being skinny, and apparently unable to keep still. As he stood, he constantly clenched and unclenched his fists, tapped his feet and folded and unfolded his arms. His was an invisible mutation, and one very, very valuable.

"This guy must mean a lot to you," he said.

Erik didn't reply.

He had expected Charles to resist. He wasn't sure why.

Although they had gone their separate ways and embraced different philosophies, they were still friends. Or at the very least, they were not enemies. Not yet. Though it occasionally appeared to be heading in that direction.

Resistance would have meant that their path from friends to enemies was complete. Only someone with a huge grudge would refuse to accept such a gift. And he expected a grudge, of course he did, but Erik was offering to put right the damage he had done. He didn't know why he expected resistance.

Maybe he didn't so much expect it as want it. An excuse not to go through with the plan.

But Charles had been so very Charles. polite, conversational, willing to invite him inside to talk. Yet he was different too. He didn't smile as much any more. Erik wondered whether that was just for him.

When he brought up the reason for his visit, Charles had gone very still, very thoughtful. A hand rubbed his thigh as he sat in his chair, not responding. Erik had left on his helmet, allowing him to keep the second half of the plan from him.

"If you can truly do this," Charles had told him, "then I can hardly refuse."

The young healer chewed on his bottom lip. His arms were folded across his chest in what looked like a defensive posture. He was young, but older than many of his students. Charles resisted the urge to read his mind, find out who he was, where he came from, and what had led him to follow Erik.

"You sure about this?" he asked, directing his question to Erik, who was sitting on the sofa looking tense and apprehensive. Charles frowned. Something about this was wrong, something didn't quite make sense. Eric was still wearing his helmet, blocking his thoughts.

"Do it," Erik told the boy.

Before he could call a stop to the proceedings, the healer reached over and gripped Charles' hand tightly with one hand, then took Erik's in the other. Physical contact enhances telepathic abilities, and Charles slammed closed his mind against a barrage of thought. Some things leaked through. Parts of the boys past, his discovery of his mutation and how that mutation worked.

The moment he realized what was happening, Charles tried to pull back his hand, but he was unable to break contact. The boy's eyes were closed tightly, face screwed in concentration. Charles turned to look at Erik, eyes wide and pleading. He knew in that moment what a fool he had been. He never should have trusted Erik. Without the ability to read his mind, his former friend could have in fact been planning anything. The story of healing abilities could have been a complete lie, instead of an... exaggeration.

He was frozen in the moment, helpless to prevent what was already happening. He felt sensation return to his legs slowly, beginning as a slight tingle that quickly spread as the nerve damage was reversed and muscle that had begun to waste through disuse was rebuilt. It was uncomfortable, not painful, but strange, and the fact that he was feeling something, anything at all, was wonderful.

He couldn't take his eyes off Erik. He watched as the opposite happened to his friend, watched the subtle and ill-disguised changes to his expression as feeling was stolen from his lower limbs, as the ability to walk was taken from him, and as the muscles of his legs began to wither before his eyes. Charles only hoped that feeling was lost before that happened.

Finally, the boy released his grip on both of them and took a step back. Charles found himself running a hand over one of his legs, relishing the ability to feel. He wriggled his toes, and they responded. He felt strong. He could run.

He didn't stand. He could have, but he didn't. Erik had been cruel to do this to him; to offer him this gift knowing that he wouldn't be able to keep it. He looked at the boy with stern eyes. "Undo it," he said.

The boy didn't look well. He had grown pale, and this face was damp with sweat. He took a shaky breath, ran his fingers through his hair, and then lost consciousness.

Charles reacted instinctively, his body knowing what to do before his mind could process. He pushed himself up, out of the wheelchair, stepped forward and caught the boy before he hit the ground.

He lowered him gently onto the floor, sparing him the bruises he might otherwise have caused himself, then stood up straight and looked down at his feet in wonder. He was standing on strong, fully functional legs. He had been told it was impossible. But then, in his world he had long ceased to believe that anything was impossible.

He looked at Erik, sitting just a few feet away, on the sofa.

"It exhausts him, using his power for something like this," his friend explained. He spoke softly, eyes fixed on Charles' own. "He'll need a day or so to recover. I trust you have a spare room?"

Charles nodded, not able to brink himself to speak. Erik was sitting very still, immobility not confined to the lower half of his body. His breathing was slow and measured, and one hand, resting on the arm of his seat, was gripping the fabric tightly, as though he was afraid that he might fall.

"Good," he said, sounding entirely too calm. "So, how do you feel?"

The question was difficult. He felt wonderful. Standing on his own two feet, master once again of his own body. He felt free, no longer a prisoner of his limitations. He felt such intense relief. He felt anger at Erik for not telling him the price of his cure, and he felt guilt, because he couldn't help but want to keep it anyway.

"I..." he said, then shook his head. "I'll arrange for somewhere for the boy to sleep, then we need to talk about this, Erik."

Charles called for help telepathically, and several of the students arrived quickly. Some new ones that Erik didn't recognize barely gave him a glance, but for the others, his presence caused almost as much of a sensation as the fact that Charles was walking.

Charles was angry. Erik could see it in the tension he was carrying. He quieted the questions with a promise to answer them later, and ushered the others out of the room with instructions to make up a room, leaving Erik alone. For a moment, the solitude was a relief, but he quickly grew irritated when no one returned. He felt strange. Unless he was looking down, the lower half of his body was just... gone. He brushed his legs with the tips of his fingers, and felt nothing. Fingers pressed harder into the flesh, searching for sensation, for something to prove that they were a part of him. Nothing.

He felt trapped, fixed in place and immobilized. It was frightening.

He could sense the metal he had placed inside the fabric of his clothing, in his shoes, his trousers. He would be able to manipulate it, allowing himself to move, after a fashion. Better than Charles could, at least. He had practiced before he came here. It had seemed so easy at the time. Now, suddenly, the idea was daunting, more akin to flying than walking, and he couldn't fly. Not really. He could hover, manipulating the sources of metal around him, pushing and pulling on them to allow him to move around. It looked impressive, and it had proved useful at times, but it wouldn't work for daily use.

Tentatively, he concentrated on the metal woven into his clothing, pulling it upward, making himself stand. At the same time, he pushed and pulled against every other magnetic material in the room. He rose from the couch, and half hovered, legs slightly bent at the knee. He pushed downward on the metal in his shoes, forcing his legs to straighten, looking almost like they were supporting him. He felt incredibly precarious, hovering in the air above his legs as though they were no more a part of him than the carpet on which he appeared to be standing. This wasn't going to work. At least, this wasn't going to work yet. In time, he would master it. Until then, he would practice somewhere where there was less chance of someone walking in on him.

Frustrated, he released his hold on the metal and fell back to the couch. He landed a little wrong, and fell to the side as he did, ending up almost laying down. He gripped the back of the sofa with his hands, and pulled himself up into a sitting position.

If felt so strange, so wrong. He had barely stopped to think about that, so fixated on how he would move around. To think, Charles had lived like this for a year. He had done this to him.

He glanced around the room, eyes finally fixing on the wheelchair where until recently, Charles had sat.

"Erik."

Erik looked up in surprise to see that Charles had re-entered the room without him noticing. "Charles," he responded.

"What were you thinking?" Charles asked. His arms were folded across his chest, and his voice was full of emotion.

Erik shook his head. "My thoughts are my own," he said, touching the side of his helmet with one hand and forcing a smile.

"It was cruel of you to offer me something you knew I couldn't accept," Charles told him.

"But you did accept it," he replied.

Charles crossed the room and sat down on the sofa next to him. He sighed, and spoke softly. "Thank you for the offer, my friend, but as soon as he is recovered, I'm afraid I'm going to have to ask our guest to reverse what he has done."

It would be so easy, to just agree, acquiesce to the understanding that Charles would never allow this to happen, and let him enjoy a day or so of being healed before things were put right. But Charles was right, that would be cruel. It was done, and it would remain done. Erik knew that he was responsible. Sooner or later, one of them would recruit a mutant that was a true healer, until then, he would live with the consequences of his own actions.

"No," he said, shaking his head. "I won't allow that, Charles. I'm too stubborn to back out now."

The telepath pursed his lips in irritation. Erik was glad of the helmet that shielded his thoughts. He had to appear decisive and certain about what he was doing. Charles mustn't know how he felt. Of course, Charles probably already did know. Even without his telepathy, he would be intimately aware of how Erik likely felt. Erik looked at his friend thoughtfully. How hard it must be for him to turn down this gift. If their positions were reversed, he wondered whether he would be able to do the same.

Finally, Charles sighed. He got to his feet and began to walk away. "Okay, Erik, have it your way," he said. "I'll have your old room made up for you. It's on the second floor, but I've had a lift installed."

Erik thought he detected a knowing smirk as he turned and strode away, leaving the master of magnetism sit on the sofa, puzzling out the best way of moving himself from his current position into the chair not three feet away. 'Well played, Charles' he thought, glad still that he couldn't be heard.