Jace's Cure.

I was lying awake at half 3 in the morning when this theory came to me.

I also thought it would make a good fanfic.

I also typed it all out, though on my phone, because my computer makes loud typing noises. At three in the morning. The same day I typed it word for word, on my computer, because I was so sleep deprived the idea of emailing it to myself didn't occur to me. Try not to judge this too harshly, but please review!

Evidently set before CoHF because it isn't out yet. ONLY READ IF YOU KNOW WHO BROTHER Z IS!

The institute doorbell rang through the entire house, so naturally Jace heard it. He lay on his bed, with Clary sleeping next to him. She looked so peaceful and carefree. Jace glanced at the clock on his bedside table. He stopped mid-yawn, his mouth staying open. Who calls at the institute at half five? Getting out of bed, yet being careful enough not to disturb Clary, he grabbed a jacket that was hanging on his door, his Witchlight stone, a seraph blade, and set off down the endless corridors of the institute.

Upon finally reaching the doors of the institute, he noticed Maryse had gotten there before him, and seemed to be having a one-way conversation.

"Yes, yes, but I don't see how this couldn't of waited until morning." Maryse snapped.

More silence, and then:

"Brother Zachariah." That would explain the one-way conversation. "I don't see how I can go to my sons room and tell him there might, just might, be a slight chance of a cure for him, yet possibilities are that it kills him? I refuse to risk my son's life."

The voice finally came through to Jaces head, with a tinge of exasperation. "I understand, although it is your sons' choice, and not yours. And Jace is a Herondale. They do as they like, nothing and no one can stop them once their mind is made up. Also, you do not need to go to his room. He is here now."

Maryse whipped around, a shocked expression on her face. "Jace?"

"You sound surprised to see me. I do live here." He stepped around Maryse, closer to Zachariah. "There is a cure?"

"There is a theory," Zachariah corrected him. "But I shall only go through with this if you are all right with it."

"You will only go through with it? Are you the one curing Jace?" Maryse demanded.

"In a way. It is a long story, Maryse Lightwood, and one you do not need to know."

"I'll go." Jace said, stepping out into the morning air.

"Jace…" Maryse began.

"No. This… fire… it is like a curse. I want to be free of it." Jace replied, turning to Brother Zachariah.

"You are not cursed. I once knew a Herondale quite well. He believed he was cursed, and pushed everyone away for nine years. He had no one, the curse didn't let him. You have people that care for you, Jace Herondale, and the fact that you carry heavens fire in you is proof that these people care." Brother Zachariah informed him.

Jace didn't quite know what to say to that. He simply turned and walked towards the carriages.

"Maryse." The silent brother said, making her turn towards him. "Take comfort in the fact that one of the brothers life is at stake too. And the brotherhood do not throw around their lives for nothing. We would not be doing this if we weren't sure it would work."

Maryse nodded as brother Zachariah walked after Jace towards the carriages.

She watched the carriage pull out of the institute gates, said a silent prayer and went back inside the institute, hoping that Jace would be all right

Jem felt alive. More alive than he had in more than 130 years. He felt a fire burning through his veins. But it wasn't Yin Fen. It was hope. Hope. If he were cured, he could leave the brotherhood, live his life, and meet old friends. Magnus, Tessa … Tessa.

Tessa.

The burning stopped, and he felt icy cold. Tessa. Tessa had had Will, had a life with Will, children with Will. He couldn't take those memories from her.

Concentrate on the Herondale boy, concentrate on Jace. He thought to himself. It is his life they are saving, not yours.

Jace felt alive. More alive than he had in years. Hope ran through him, keeping him warm. Jace thought back to the conversation Maryse and Brother Zachariah had had before.

"You will only go through with it? Are you the one curing Jace?"

"In a way. It is a long story, Maryse Lightwood, and one you do not need to know."

What WAS this story? Was it to do with his cure? He intended to find out.

The carriage stopped. They had arrived. Jace opened the carriage door and stepped out, and saw brother Zachariah. His words echoed through his mind.

And Jace is a Herondale. They do as they like, nothing and no one can stop them once their mind is made up. Jace smiled to himself. It described him perfectly. He liked it, even if he did go by the name of Lightwood.

Brother Zachariah appeared behind him. Jace jumped, and cursed inwardly. He didn't like to admit it, but even he was freaked out by the way the Silent Brothers walked.

"Welcome to the Silent City."

Jace shrugged. "I prefer City of Bones."

There was the slightest of silences before: "The Silent City has many names, Jace Herondale. Many shorten it to Bone City."

"Ahh, but, Zachariah, there is giving a place a nickname and then there is pure laziness." Jace replied, as they walked towards the entrance.

Zachariah grinned. The second it had appeared it had gone, but Jace still caught it, puzzled. A Silent Brother grinning? That was something you didn't see often. They stopped at the doors, Zachariah hesitating.

Brother Zachariah turned to face him. "Jace, you can leave if you want. You do not need to risk your life. The fire is something you can live with, and may even be useful at times. It is not killing you, it is not life threatening, like Astriol-" The Silent Brother stopped himself, a spark igniting in his eyes.

Jaces mouth turned up at the corners, remembering an old piece of paper in the box that was his fathers, writing so faint he could barely make out the words. He had realised it was a song, and it was attached to another note, saying to sing this at all times 'Demon Pox' is mentioned. Jace's smirk changed into a rather demonic grin. He had memorised the song, it was funny yet awful at the same time.

"Astriola. You were going to say Astriola. THAT is Demon Pox. And, upholding the wish of my ancestors..." He never got to finish that sentence.

"Ah. You learned the song." Brother Zachariah had opened the doors and they were walking through the endless corridors.

Jace raised an eyebrow. "How do you know the song?"

"I was there when it was first performed. I was also hit on the head with a scroll by one of your ancestors at the time."

Jace raised his other eyebrow, and his grin returned. "And next you'll be telling me you know the song off by heart."

"Demon pox, oh demon pox, Just how is it acquired? One must go down to the bad part of town until one is very tired.

Demon pox, oh demon pox, I had it all along—not the pox, you foolish blocks, I mean this very song—for I was right, and you were wrong." Zachariah informed him.

"Then of course, there was the maniacal dancing on the table, which I do hope you were not going to include."

Jace opened his mouth, and then closed it. DAMN. That was the song gone. He decided to change the subject. "What is the cure?"

Silence. About a minute later Zachariah and he neared a portal.

"The fire is to be…transferred from you to another person." They were right in front of the portal. "Think of Idris." Zachariah told him and he stepped into the portal. Confused, Jace followed him.

"This," Zachariah gestured as to where they had come out, "Is the real 'City of Bones.'"

Jace smiled at how the Silent Brother had called it Jace's preferred name, yet then thought back to the cure, and again to Maryses conversation, his smile gone.

"You will only go through with it? Are you the one curing Jace?"

"In a way. It is a long story, Maryse Lightwood, and one you do not need to know."

Jace understood. The fire would be transferred between him and Zachariah.

"But, if it is being transferred, the other person must have demon blood or presence, mustn't they?"

"The person does." Zachariah answered in a clipped tone, telling him the topic was over.

"You have demon blood?" Jace let the words leave his mouth before he even thought about them. (A/N: Yin Fen is powdered demon blood. Brother Z still has some in his body)

The Silent Brother stopped in front of large double doors. "What makes you think that the fire is being transferred to me?"

Jace snorted. "This wouldn't be the first time you've risked your life or the law for me. I shall be very shocked if another person has been chosen."

To that, the Silent Brother seemed to have no reply, and he opened the doors and he and Jace walked inside. And that was when Jace passed out cold.

Jace's eyes fluttered open. Everything was blurry and his hand felt numb. "Jace!" He heard someone yell. "Alec! Jace is awake!" Izzy.

"Jace?" He heard someone ask. Alec. He felt his hand being gripped and strength washed over him. Ah, the joys of having a Parabatai. The drawing-on-another's-strength had its perks.

"I'll get Clary." Jace heard Izzy say, before a weight left his bed, and then the room.

"Did it work? Am I cured?" Jace asked Alec.

"Well," he saw Alec shift, "you are gripping my hand, and I'm not burned so…"

Jace lifted his head and saw it was true. He also saw an ugly burn scar that covered his entire right hand. It's a good thing I'm left-handed, he thought.

"Alec, what happened?" Jace asked him.

"Well, you know more than I do. You woke up and were taken to the Silent City in Idris by brother Zachariah, and then two days later you came back, with a different Silent brother." He said. "He's with Maryse now." He added as an afterthought.

Brother Zachariah.

'This wouldn't be the first time you've risked your life or the law for me. I shall be very shocked if another person has been chosen.' Jace felt as in someone had thrown a bucket of ice over him. He attempted to brush it off. You didn't know him, Jace. It's not a big deal. Shadowhunters die every day. But he couldn't get rid of the feeling.

"What isn't a big deal?" Alec asked, curiously.

Damn. Jace realised he had spoken out loud. He was, however, spared answering, however, by a Silent Brother, Maryse, Clary and Izzy.

"Jace." Clary breathed, running over to him as if he was the only thing that mattered to her. Beside her was Izzy, gliding gracefully compared to Clary's stumbles. They both started talking to him at once, but that wasn't the conversation that held his interest. It was the one between Maryse and the Silent Brother, which seemed to be coming to a close.

"…and then he will be fine?" Maryse finished.

There was silence, which was probably the Silent Brothers reply, and then: "Thank you brother Enoch."

Enoch nodded and glided over to Jace.

"Where is brother Zachariah?" Jace demanded.

"That is a personal matter of the brotherhood, Jace Lightwood, one that you need not concern yourself with."

Lightwood. Only Silent Brothers used surnames in conversation, and Jace was used to being called a Herondale by Zachariah. It seemed odd being called a Lightwood, even though Jace had asked the brotherhood to call him such.

"He gave his life for me, I'd say the matter concerned me." Jace shot back.

Out of the corner of his eye, he saw Maryse raising an eyebrow, Clary looking shocked, and Izzy and Alec exchanging looks.

"You will need to stay in bed for at least twelve hours." It seemed that brother Enoch had ignored his last comment. The Silent Brother turned and walked out of the infirmary.

"Jace…" Maryse asked him. "What DID happen, in Silent City."

Jace told them he couldn't remember, since he had blacked out. When asked if he could remember before that, he told them no. He COULD remember before the room perfectly well. Talking of demon pox and sacrifices, thoughts of hope and future, and the Silent Brother smiling. It would have seemed worthless to them, but to Jace it was a day he would never forget.

Ave Atque Vale Zachariah. Jace thought to himself, before immersing himself in the conversation before him.

A/N: I know Jem didn't die, but the point was he had left the brotherhood, meaning he couldn't tell Jace he was fine/ escort him back to the institute. I will add an epilogue eventually, expect it in a few days ;) PLEASE REVIEW! I'LL MAKE MY DAY AND SHOW ME IT'S WORTH TYPING AN EPILOGUE.