Waking after a few hours' rest, Rose laid blinking up at the ceiling above her bed. There was no confusion about where she was when she woke. The TARDIS's hum stayed with her even in her sleep, part of her always aware of the ship. It was as much a mystery to her as the Doctor was. Her bedroom had been completely dark when she went to sleep, but was the comfortable dim of dawn when she woke, despite there being no windows. It didn't feel like it simulated regular daytime hours though. The ship's light didn't wake her; it was like she woke the ship's light. What gave her that impression, she wasn't sure, but she felt rather confident in her theory. Then there were the clothes that the TARDIS selected for her - all her size and in the styles she liked on Earth. More than that though, it had her favorite type of shoe from Clavix, shampoo with a floral scent she liked from Weaspin, and when she wanted biscuits to go with her tea during the night, she turned around and found a package of her favorite biscuits that she used to have imported from Sentrin Prime. If she'd ever had any doubt that the TARDIS was telepathic, it had vanished extremely quickly. Every time she thought, 'I wonder if you've got…' or 'I wonder if you can…' the TARDIS provided what she asked. She really didn't care for the idea of someone or something in her head, but as the Doctor had told her, the TARDIS did feel friendly and was generously accommodating. The Doctor himself was generally friendly and accommodating, too, but his people skills really needed work. She hoped he was in a better mood that morning… or whatever time it was.

After washing and dressing for the day, Rose set about making breakfast. She decided to make enough for the Doctor, too. She wanted to start the day, and this whole new living arrangement, off on the right foot. As though summoned by the scent, the Doctor appeared in the doorway just as Rose was plating the food.

"Hello," she greeted with a smile. "Hungry?"

The Doctor was simply surprised at first, but quickly returned her smile. "Sure."

He seemed quite pleased with the meal, causing Rose to wonder what he ate when he was on his own. She couldn't picture him doing much cooking.

"Sleep well, then?" he inquired.

"Yeah, and feel much better for it. Usually I feel sluggish in the morning after taking a sleep aid. I don't think I've ever woken up feeling so energized… well, except for mornings of holidays and festivals."

"Just need the right sleep aid. I'm glad it helped."

The Doctor seemed in a good mood, or at least not a bad mood. He was smiling and his voice was light. Rose was reluctant to do or say anything that might change that, but she wanted to get back to what he'd been avoiding the night before. She just needed to go about it carefully. "So what's next for today?"

Even that was enough to flip the switch. He didn't look angry or irritated, but his expression still hardened. Rose couldn't take it anymore and completely snapped.

"Would you bloody stop that?!"

Her sudden change took the Doctor completely by surprise and he gaped at her in confusion. Rose felt a bit of satisfaction in that. See how he liked sudden hot and cold.

"I feel like I can't say anything to you. Happy, teasing, smiling and then the next second you're closed off or fuming or brooding. I feel like I'm walking on eggshells. You want to help me and I thought I'd be getting answers considering you said we'd figure this out, but you clam up and won't say a thing. Bloody hell, you even sent me to my room! Twice! And the second time I had been minding my own business. I thought we were just having a conversation. You had come to me.

"I've been trying not to press, but I can't even ask what we're doing today without you closing off. You can't invite me in and shut me out at the same time. You've got to pick one."

The two of them stared at one another from across the table, their expressions hard. While Rose was clearly upset, the Doctor was inscrutable, his face completely void of expression. It was maddening.

"Are you done?" he asked evenly.

"No." Rose was done shouting, but if she was speaking her mind, she was going to finish. "I want to get along. We've always gotten along brilliantly. I don't want to upset you and I'll try hard not to, but I get the idea that that's not going to happen until we get past this hurdle. There's something you don't want to tell me so you're avoiding it, pushing me away. But this is about me. This is my life. Whatever tests or information you have, it's about me and I have the right to know. Right?"

The Doctor was staring down into his mug and didn't respond right away. After a moment, he pushed out of the chair and carried his dishes to the sink. Rose was afraid he was going to leave without saying anything, but he sighed heavily, looked over his shoulder at her, and quietly beckoned, "let's have a look at it then."

Rose hurried to put her dishes in the sink and follow after. When they arrived back at the infirmary, it was slightly bigger than the day before. Two comfortable armchairs with throw pillows and a small coffee table in one corner of the room were new additions. Rose wasn't sure where she was supposed to go and just waited for the Doctor who seemed uncertain himself. He gestured toward the armchairs, but as soon as her bum hit the seat he changed his mind.

"No, just… over here." The Doctor stood at the desk with the computers, but kept his back to them, leaning against the desk as he silently reviewed his thoughts. "'m not sure where to start."

"Well… what tests did you run yesterday?" Rose suggested. It was clear that whatever the Doctor found out wasn't good news and she was terrified at what it might be, but she believed she did a rather good job at hiding it.

"Nearly everything. Your iron's a bit low, by the way."

"Okay… right." Rose sighed and tried again. "There were some tests you focused on. You said one answer answers others or something. Some things are connected. The slow aging and fast healing and stuff?"

The Doctor ran his hand down his face and finally turned to the computer and brought up a long list. Each line had one or two words followed by a number. "Radiation levels," he explained. "Most are just background radiation, things you pick up in everyday life, from the sun, the air, the food you eat. But there are three things here that very few humans would ever come into contact with and those are artron, chronon, and zygma radiation. Those are found in the time vortex. Humans set up the Time Agency in the 51st century and any agent that traveled through time had to go through the vortex and was exposed to those elements, as does any human that travels in the TARDIS. Low levels though. Background radiation. My people are a bit different. We created the time vortex and over a million years of exposure to it changed our biology. Time is written in our DNA, artron in particular. We produce it. Babies are born with a certain supply and it increases over time. There are instances, such as recovering from severe injuries, where we lose some, but a certain supply is necessary to our survival. I've never before seen a human with more than 8 atto-Omegas, and he had traveled for decades. Mine never drops below 48 atto-Omegas, and as it stands now, I'm at 78. Highest I've ever gotten was 92. You… You, Rose Tyler, have an artron energy level of 883 atto-Omegas."

Rose suddenly felt a bit ill. "That's… bad, isn't it?"

"Well, I can't say it's a good thing, but it doesn't seem to be harming you. In fact, the artron energy is what's protecting you from getting ill. It boosts the immune system." He brought up another screen which she assumed displayed test results regarding her immune system. "It could also explain faster healing if your body knew how to use the artron energy in that way. Human bodies shouldn't know how to do that, but if they did and if they had enough energy to use for that purpose, their artron levels would go down."

"Which means, if my body could and did use artron to heal, then my artron level used to be higher?" asked Rose. She fiddled nervously with her earring, knowing that bad news was still to come. It was disconcerting to learn that she was filled frightening, unexplained levels of radiation, but there didn't seem to be harm in it.

"Yes. If you were using artron to heal, it would be depleting the stores you had."

"But how did I get it? From the time vortex, yeah? When I'm displaced, one time and place to another, I've got to be going through the time vortex. But how come I've got so much?"

"Good questions." The Doctor nodded in approval. "You did likely pick them up from the vortex, but not from being displaced. Those energies are what you use when you're displaced. I told you before, I thought the means and trigger were in you. It's the zygma energy that conducts it, that pulls you into the vortex, and the chronon and artron see you through it. People can't survive the vortex unprotected – their devices shield them – but you manage to make it through unshielded and without device. I can't explain that."

"Well…" Rose said slowly, taking a moment to organize her thoughts. "If the energy is making it happen, is there any way that you can like… drain it or something? Take away the energy so I can't do that anymore?"

The grim look on the Doctor's face didn't make her very hopeful. "Not without serious risks. We need to understand the trigger first. You're thinking – pull the trigger on an unloaded gun, no problem. But I think of the trigger as more like a spark. Think of the trigger like a surge of electricity. The time energies conduct and insulate the spark. Without them…"

"A spark? But I thought you said it was like a hypnotic trigger," Rose worried.

"No, I used stage hypnotism as an analogy. What I said was that the trigger was a subconscious response," he corrected. "The problem is, I can't understand how the trigger works. We know what sets it off, but not what's behind it. Of course, that's not the only problem. The problems are numerous. This 'Bad Wolf' did a lot of tampering."

"Meaning…?"

The Doctor rolled his eyes and looked ready to make a sarcastic remark, but refrained. Closing his eyes, he let his exasperation fall away, leaving remorse behind. He wasn't upset with her, he was upset on her behalf.

"This 'Bad Wolf,' whatever it is, is powerful. I can't fathom how it's influenced and altered all that it has, but it's significantly affected your life," the Doctor told her softly.

Rose forced a small smile. "I've noticed."

"I know." The Doctor's speech was grave and his eyes remorseful, and there was gentleness when he explained. "It affects the events in your life, but what I meant was that it affected your life itself - you. It's more than just being filled with time energy. It's part of you."

The Doctor pulled up another image on the monitor, a rotating model of a DNA double helix.

"Your DNA, as simple and complex as any other human's. That would be plain to anyone having a look at it. Except that's not all there is to it. You remember how I said that my people had time written in their DNA? So do you." The press of another key revealed a third strand in the helix. It was colored slightly differently to more easily distinguish it from the other two and it appeared to be bound to one of the other strands. "This is what your DNA really is. A triple strand. The reason no one could pick it up is that they didn't have the proper equipment. The third strand is made of temporal matter so it's only detectable on temporally aligned scanners."

"It changed my DNA," Rose stated quietly, her expression distant. "Does that mean I'm not human?"

"It depends on how you look at it, but I think of it as sort of 'human plus.' At the core, you're still human. The extra strand is temporal so, while very real, it's not the same as solid matter. It's also more of an addition than an alteration."

"Is that what you're like though?"

"No, I'm something else entirely. We may look similar on the outside, but we're very different on the inside. My DNA is much more complex. Three solid strands and a temporal one." The Doctor still spoke softly, gauging Rose's reaction. She looked hollow, yet still pensive.

"So what does it do then?" she inquired. "If I'm still human, how does that make me different?"

"Time. It affects you differently." The Doctor paused, searching for the best way to explain. "I explained that artron energy is what helps you heal more quickly, but it's not the energy that heals you. The artron affects the time it takes for your body to heal itself. The artron doesn't magically seal a wound and doesn't make your body function any faster. It affects the time it takes to heal. It's difficult to understand without really understanding time itself."

Rose was clearly struggling with the concept, but decided to settle for the Doctor's explanation, at least for the moment. She knew that couldn't be the only thing affected. "What else?"

"Your time sense is stronger. Humans in the early 21st century still teach that they have five senses, which I'm sure you're familiar with. But there are loads more: temperature, hunger, pain, direction, ect. Then there are others that aren't as strong and so not as obvious: the ability to sense objects and people in a room, low level telepathy, time…"

Rose could tell that the Doctor found this information fascinating (which Rose could agree) and he liked sharing it, but she also got the idea he was stalling with his explanation.

"People talk about an internal clock that helps them wake around the time they desire, especially if it's the same time every day. But they can also sense the passing of time while awake. If I walk into a room and ask someone how long they've been there, 5 minutes or 50, even a small child would be able to confidently give a correct answer. Last night, you were in the console room and I asked how long you were there. You said about 45 minutes, but I suspect you could have given a more exact time. I suspect you know almost exactly how long it took you to make tea. More than that, I suspect your calculations concerning your age are pretty accurate. You likely sat down and wrote it out at some point, but I'm guessing that the conversion of Rabsor time measurements to Earth time measurements came rather easily. Well, the math might have been difficult, dunno, but I bet your initial guess came easily and was surprisingly accurate."

The Doctor looked at her expectantly, waiting for Rose to confirm or deny his suspicions.

"42 minutes," she answered. "The water for tea heated almost instantly so it was only 5 minutes from the time I entered the kitchen to the time my tea was prepared. Not 4 or 6 - it was 5 minutes."

The Doctor grinned with pride.

"What else though?" Rose pressed on.

The Doctor's gaze averted and his smile dropped.

"Yeah, you don't want to tell me. I get that. You have to tell me though, so out with it." Rose didn't mean to be so commanding, but she was anxious and couldn't take the suspense anymore.

"It's the aging thing," the Doctor confessed. "You've noticed that you age slower, but that was aging as a child. It's in your temporal DNA. It affects your cells' maturation and degeneration. It takes longer for your body to mature, but once it's completed the adolescent stage, your temporal DNA will prevent your body from changing or degenerating. You'll continue to produce artron like me and it will sustain you as you are."

"So I'm not going to age anymore?" Rose asked with concern.

"Maybe a bit more, a year or two, because despite your actual age, your tests say you're still at the tail end of adolescence. After that though, you'll stay the same."

"But for how long? I can't be like that forever." Revelation of what this could possibly mean finally hit Rose and she was quickly becoming distressed and fearful.

"I'm not sure, but it will significantly extend your life." The Doctor's sympathy, though kind, was making Rose even more anxious. Such an expression only made her fate feel even more dreadful.

"What about you though? You're different, but you have temporal DNA, too. You're not a young adult, but you live a long time. Am I like that? Will I live for centuries like you? You're sure I won't age like you do? I mean, how do you know this stuff?" Rose was becoming even more panicked. The tremor in her voice and her quick shallow breaths revealed the severity of her anxiety and the Doctor guided her into one of the armchairs, seating himself in the one across from her.

"I know this is overwhelming, terrifying even. You've grown up with expectations. The people you've grown up around, even different species, go through an aging process. I'm sure you've considered you might have a bit more extended life, considering you age more slowly, but you didn't expect this. It's scary and might be hard to come to terms with, but you've got to try to calm down a bit. Worrying isn't going to help. Try not to think about the distant future because that's a long way off. Plenty of time to adjust." The Doctor was at his most tender and soothing yet, even more than the day before when he had assured her he'd been looking for her.

"It's difficult to guess an age expectancy for you because I've never seen anything like this before. Your temporal DNA is similar to mine, but not exactly the same. I've studied it in great detail, marking the differences in us. I then compared those differences to the DNA of other species. I don't know of any others that have temporal DNA, but there are some that don't have any growth stages after they reach adulthood. Their bodies still degenerate, but their hormones don't trigger any more changes. In some of the places you differed from me, you matched with two of those species. Longevity is nearly impossible to guess, but I believe, barring accidents, you've got at least a couple centuries ahead."

Rose was completely still in her chair, her thoughts racing so quickly that she wasn't able to hold onto one long enough to examine it properly. Fragments of thoughts just kept repeating: Won't age, not human, centuries, won't age, not human, where will I go? won't belong, centuries…

"I need to lay down." Her toneless voice echoed her hollow expression and her movements were mechanical as they carried her from the room. The Doctor understood her despair all too well and grieved with her. There were many people in the universe that desperately desired long life or even immortality, but they didn't understand. The Doctor wouldn't wish it on anyone.

Poor Rose understood, just as he'd guessed she would. It was hard to tell her, but it was right for her to know. If that was true though, it would make it wrong to withhold anything. Right or wrong, the Doctor didn't have the heart to reveal everything. In truth, he didn't know how long she could live, but he knew that even if they could stop her from being displaced, she'd still be able to cheat death. Rose had at least one potential regeneration. She could easily live more than a couple centuries in her current body, only to regenerate into another. Perhaps even another after that. There was no way of knowing. After Rose's reaction to what he'd told her, how could he explain that on top of it? He couldn't.

A/N: Thank you so much for the reviews!