A/N: This story was inspired by watching The Bourne Ultimatum. That means it is slightly derivative, but I hope it is still interesting enough to read. While it began as an idea of Tim having another identity, it has taken so many turns that it's hardly recognizable as what I thought it would be in the beginning. Spoilers for season four.

Disclaimer: I own nothing of NCIS, it's characters, nor the franchise. I just wish I did.

Prologue: Creation

"We need someone in NCIS."

"Why? It's military only. We haven't had to deal with the military for years."

"It's becoming more and more important to have ears in every federal agency. That includes NCIS. You never know when something will happen and we'll need information."

"Do you really think that is necessary?"

"Yes."

"Why now? And why not just use one of your own agents?"

"My agents are too well-known in federal circles. They'd give themselves away somehow."

"How?"

"By being too good. We need a so-called sleeper agent. Someone who will perhaps never even know what they are. Someone we can call into service–or remove from service–at any time."

"I don't like what you're proposing. We all have the same goal, after all."

"You'd rather be taken by surprise when a case comes up in NCIS that relates to us? You'd rather have the people at NCIS find out about us and open us to full scrutiny by the harsh light of day? We don't work like other people. We can only survive in darkness. Forget about the morality of the situation and tell me if you think it's possible."

"It's possible. What you're proposing is easy enough, in theory. Suppressing the original personality will be difficult, but it's possible if you get the right person. Once that has happened, it is only a matter of placing a small compulsion in the mind along with orders to forget about each report as it happens. He... or she..."

"He."

"He will be, to his knowledge, completely loyal and a normal employee of NCIS. We can place a desire in his mind to join and to get into the main headquarters."

"Good."

"I take it that you have someone in mind already?"

"Yes. Here's his file."

"Thomas Elton Gemcity. Interesting name. It almost sounds made up. Why him?"

"He goes by Thom. Thom E. Gemcity. It's his real name, and he's perfect. He has no family to speak of anymore. He tested at genius levels in high school but dropped out when his parents died to try to take care of his baby sister. When she was taken from him, he ran away from foster care and has been essentially homeless for the last five years. His sister grew up in another loving family. She doesn't remember him except as a vague presence. No one will notice his absence, and he has the innate intelligence we'll need to get him employed, albeit a bit rusty at the moment."

"We'll need to create an entirely new identity for him, and educate him to fit what we decide to do. We can't leave any holes. If there's a single fact out of place, the whole persona we're creating could become unstable and collapse. I'll leave that up to you and your... people."

"Done. How much time will you need to get set up?"

"Two days. We can start deconstructing his personality as soon as we have him, but we'll need to have someone to put in his place almost at once; so you'd better have it ready when you give him to us."

"We'll be ready."

"You've already started, haven't you."

"Of course."

"One word of warning, however."

"Yes?"

"It is impossible to completely get rid of the original personality. What we'll be doing is putting an overlay on the existing person. We can't destroy Thom completely. Pieces of him will flare up at unexpected times. That can't be avoided. It will be better if you make his new personality at least slightly similar to the original. Also, he should have a handler."

"Already planned for that."

"Someone who will be expected to be close to him, a family member if possible. A younger sister perhaps?"

"Why younger?"

"He'll be more likely to be protective and close to a younger sibling, particularly with his current background. That feeling will still exist. He'll feel responsible and if it's a sister rather than a brother, there will be less possibility of invented sibling rivalries."

"We can do that."

"She'll have to know his personality intimately. In fact, she should be in on the creation... that is if you aren't finished already."

"I know just the person."

"You've been planning this for a long time, haven't you? You already knew what I'd say."

"I did need to hear it from your own mouth, and you gave additional information that I didn't have before, but yes, it's been in the works for months."

"When will I have him?"

"Thom will be in your hands in two days; so you'd better be ready by then."

"We'll be ready. The real question is will he."