Prologue - Paris, France

She was not easy to kill. It took a long time for the last of her regenerations to come to an end, longer than he'd anticipated. Much longer. The boy had come back, had seen his mother's face contorted in agony, seen the blood of ten regenerations spread across the bedroom. Had seen his mother's murderer standing by the window, eyeing his handiwork with academic interest. Had seen all that, taken it in, and run, all before the killer could do more than meet the boy's stunned, accusative eyes and smile. He was fast, the killer would have to grant him that.

But not so fast that he couldn't be found. Sooner or later, he would be found.

Found, and destroyed in much the same manner as his mother.

The Master looked down and brushed a strand of dark hair away from his victim's unseeing eyes in a curiously tender gesture. "Sweet Romana," he murmured. "I did so hate to do this to you. But it was the only way; Time Lords are exceedingly difficult to kill. You gave me no choice when you refused to tell me what I wanted to know." He smiled. "And you've given the Doctor yet another reason to come look for me. Well done."

Somewhere in Space

It was a nice, quiet little planet, the young woman known as "Ace" had to admit; very pretty with its rivers and forests and complete lack of life either intelligent or dangerous. Very nice, very quiet–and very boring.

When the Doctor announced that he needed a rest, she'd taken him at his word, but secretly believed they'd end up somewhere else, hip-deep in some crisis or other. When they had actually materialized where the Doctor wanted to go, she'd been surprised, but then assumed that something was going to threaten either them or this place.

So much for secret beliefs. Peace and calm had never appealed to her except during the middle of being shot at or captured, when she longed for it with all her soul. When it had actually been achieved, she conveniently managed to forget this fact and longed instead for action.

It didn't help that the Doctor had been in a funny sort of mood lately, reminiscing about this adventure or that, talking about past companions, some of whom he had almost never mentioned in all the years they had been together--nearly five, Ace realized. Longer than most of his other companions had lasted, from what she'd gleaned from the TARDIS database and his own, less-reliable reminiscences. Five years, and in all that time, the Doctor had never returned to visit any of the people he mentioned so fondly. Not even the ones on Earth. It wasn't as if they never spent any time on Ace's home planet, either; sometimes it seemed as if that was the only place they visited!

Unfortunately, whenever they did attempt a simple visit, there ended up being some kind of world-threatening disaster they had to prevent that left the two of them too busy to think beyond the next moment. And when everything was over–including the shouting–they somehow managed to take off for the next calamity without remembering the original reason for the visit until it was far too late.

Now, it seemed that all that procrastinating was taking its toll, at least on the Doctor's subconscious. He'd taken to absentmindedly calling her Sarah Jane, or Leela or Tegan; every now and then it would be Victoria or Nyssa, and once it was Romana. He'd clammed up after that one, though; the Time Lady was one of the few companions he hardly ever spoke about, and when he did it was in an abrupt, irritated tone that could have been due to any of a half-dozen reasons, up to and including the fact that she'd basically abandoned him to stay in E-Space. Which Ace saw as mere poetic justice, considering the amount of companions he did the same thing to. Not abandoning them in E-Space, of course, just sort of leaving them and trotting off to the next available disaster.

She'd tried teasing him back into a good mood, calling him "Professor" for his absentmindedness, but his only reaction was to growl irritably that he didn't call her Dorothy, did he, and stalk off in offended silence.

That had certainly shut her up, especially since she hadn't realized he knew her real name. She would've sworn Mel hadn't told. But she had more than that to worry about. The Doctor's reaction–or rather, over-reaction–to her innocent teasing puzzled her, a puzzlement that only deepened when they finally plunked down on a planet in the middle of galactic nowhere and simply sat for nearly a week.

Ace had had enough. Enough of his moodiness and the everlasting, boring peacefulness of this place. It might be an Eden, she decided as she looked around the terrain with a critical eye, but it was an Eden sorely need in of a snake and an apple to liven things up. Especially since the Doctor had gone so far as to flatly forbid her to get in any target practice, even with a marvelous sand-pit nearby to soak up the explosions. With this irritable thought, Ace walked, then trotted, then finally broke into a run for the nearby river. Her irritation had blossomed into full-fledged fury, and she felt the need for physical exercise to work it off. When she reached the bank of the shallow, muddy-yellow river, she quickly stripped off her sneakers, jeans and t-shirt, and dove in.

As she headed for the opposite shore, Ace fumed silently over the Doctor's moodiness. By the time she actually reached the far shore, however, her fury had abated as she reached the conclusion that it wasn't really the moodiness that was bothering her; it was the as-yet unrevealed source of that moodiness. Ace hated not knowing what was going on.

The Doctor was standing on the bank as she reached the shore. Her clothes, which she had left helter-skelter on the grass, were now folded in a neat pile by his feet, the toe of one sneaker just peeking from beneath her jeans. The Doctor was holding a towel in one hand and had the other hidden behind his back. "Haven't you forgotten something?" he asked mildly, bringing the hidden hand forward. It held her bathing suit.

Ace blushed crimson. She was still shoulder-deep in the murky water, but it felt like no cover at all for her underwear-clad form. "Well, I can't bloody well put it on now, can I?"

The Doctor blinked. "No, I don't suppose you can," he agreed. He looked around, then spied a bush growing over the water's edge. He walked up, threw the towel over it, and placed the bathing suit and her clothes on the ground before retreating to the opposite side. "There!" he called merrily once he was out of sight. "Modesty is preserved!"

Ace shook her head in exasperation, then grinned in spite of herself. It was only a matter of moments before she had scrambled out of the water, donned the suit, and pulled the towel down to dry her hair. The straight brown tresses reached nearly to her waist now, she noted absently before singing out: "I'm decent!" She spread the now-damp towel on the grass and threw herself belly-down on top of it.

The Doctor walked back around the bush and slowly settled on the ground next to her. They sat in comfortable silence, their first in days, simply enjoying each other's company and the afternoon sunshine of an alien world. Ace's bad mood had completely evaporated and she caught herself wondering just what she'd been so upset about in the first place. Moodiness, she reminded herself, but was unable to dredge up her previous irritation. She shrugged mentally. Just as well.

When the Doctor finally broke the silence, it was with a completely unexpected question. "How old are you now, Ace?"

"Five years older than I was when we first hooked up," she replied after a moment spent shifting mental gears; she'd more than half-expected the Doctor's first words to be some sort of oblique apology for his moodiness. "Why?"

"Has it been that long?" the Doctor asked in surprise, completely ignoring her last question. Ace nodded. "My! How time flies!" He turned reflective. "I'm almost 900 years older than you are. You see a lot in 900 years..." His voice trailed off.

Ace's expression turned sour. "Cor! You're not going to take another trip down memory lane, are you? It wouldn't be half so bad," she grumbled, "if you'd just get to the bloody point when you do!"

The Doctor had all his breath ready for an indignant response; Ace could actually see it trembling on his lips. He surprised her again by turning it into a rueful laugh. "I suppose I have been wandering that road quite a bit lately, haven't I," he responded with a shake of his head. "I don't really even know why; it's just that--" he groped for the proper words "--every now and then, my past seems to catch me up all at once, and I can't shake it loose."

Ace nodded sagely, although she had only the barest glimmering of what he meant; as he'd pointed out, she had far less past to catch her up than he did. She was more comfortable dealing with the here and now, no matter when or where that happened to be, and it had always seemed to her that he felt the same way. "What do you usually do when that happens?" she asked, intrigued by this rare glimpse into emotions the Doctor usually kept hidden away.

"Find some trouble to stick my nose into," came the prompt--and surprisingly honest--reply. It was a day full of revelation for the Doctor's young companion; she was used to more evasiveness from the Gallifreyan regarding his feelings, and wasted no time in telling him so. The Doctor laughed out loud at her tart observation. "Yes, well, it gets to be a bit of a habit after a while, being mysterious. 'Keep 'em guessing' has been my motto for several lifetimes."

"So why change now?" Ace asked curiously, rolling on her side and leaning her head on one hand as she stared up at him.

The Doctor frowned and shrugged. "I don't know," he admitted. "Maybe it's just time for some new habits. What do you think?"

"If you want my approval, you've got it," came the prompt reply. She sat up with a grimace. "It gets tough, sometimes, knocking about with someone who has all the answers and won't tell." When the Doctor opened his mouth to object, she quickly amended: "All right, someone who seems to have all the answers, then."

The Doctor grunted, whether in irritation or amusement, Ace wasn't sure. Another moment passed in silence before he spoke again. "Did I ever mention that I have a granddaughter?"

Ace had thought she was getting used to the Doctor's lightning-quick subject changes on this most unusual of afternoons, but this one threw her completely for a loop. She struggled unsuccessfully not to show how staggered she was by this revelation as she asked with elaborate casualness, "Oh? Son or daughter?"

It was the Doctor's turn to be thrown off by an apparent non-sequitur, Ace noted with secret glee; this time he was the one groping for the thread of thought she had followed. "Now there's something I haven't thought about in a long time," he murmured, his eyes narrowing as he gazed into the unseen distance of his own past. A tiny smile tugged at his lips. "I left Susan–my granddaughter–on Earth, to settle down with that boy…David, that was his name. Ian and Barbara were with us then," he continued, his voice edged with a faint note of disapproval. "Susan would insist on going to school on Earth..."

"What happened to her parents?" Ace interrupted. Fascinating though the snippets of information the Doctor was giving her might be, he still hadn't answered her first question.

"Well, they–I mean, of course they–" A frown appeared on the Doctor's face as he struggled with his uncooperative memory, searching for a face or a name to answer Ace's question. "This can't be possible," he exclaimed, sitting up in dismay.

"What is it, Doctor?" Ace asked.

He didn't seem to hear her question, or even notice her presence as he jumped to his feet and began to pace back and forth, brow furrowed in thought. "I don't believe this! I just assumed the memory was there, that I simply hadn't bothered to take it out and look at it. There were always plenty of other things on my mind," he added, as if that were some kind of explanation.

"Doctor, I don't have a clue as to what you're going on about," Ace complained. "Is this one of those things you're going to explain to me eventually, or just another one of those times when I'll never be told what's really happening?" Her voice rose resentfully at the end of the question.

The Doctor blinked in mild surprise. "Do I do that?" he finally asked, momentarily distracted by the vehemence in Ace's voice. She nodded. "I gather I do it...rather frequently?" Another emphatic nod. The Doctor quirked an eyebrow, then turned to gaze out over the placid waters of the river. Ace recognized his "thoughtful face" and settled back on her elbows and waited. She wasn't by nature a patient person, but five years of traveling with the Doctor had forced it upon her.

She was rewarded for that carefully cultivated patience far sooner than she anticipated. The Doctor sat back down on his haunches and rested his arms on his knees. "Another bad habit I seem to have fallen into," he mused. "It would appear that I have more of those than I thought." He sighed. "As for what I'm going on about this time, I've just realized that I don't know who Susan's parents are. I don't even remember," his voice caught slightly, "if I have a son or a daughter; what's worse, I don't even know who that child's mother might be. Nor do I remember how she came to live with me on the TARDIS."

Ace's forehead wrinkled in a frown. "How is that possible?"

The Doctor shook his head. "I don't know. It's as if those memories don't exist, as if they've been...erased."

Ace fought the chill that went over her. "You mean like from regenerative trauma?" she suggested, groping for a possibility she could understand.

The Doctor's expression remained troubled. "I suppose it could be that, but I doubt it. I never could resist meddling with my own past; at some point I must have realized there was a rather significant portion missing. I mean, it isn't the same as chucking memories about planets I've visited, is it? One doesn't just discard memories of one's own family."

"Well, there were times I wanted to ditch any memories of my past," Ace said, pulling a face. "D'you think it's because you have bad memories, that you were willing to let them go?"

"They'd have to be pretty awful, if I did," the Doctor pointed out. "It just doesn't seem like me–any of 'me'–to do such a thing. Of course," he interrupted himself, "it could have been a decision I made when I still had Susan, or right after she left me. Perhaps I thought it was for the best." He still sounded doubtful.

"Well, there's one way to find out," Ace said. The Doctor raised an inquisitive eyebrow. "Go talk to yourself."

"It's a rather trivial reason to break one of the highest laws of the Time Lords," the Doctor replied drily, but Ace could tell he was thinking about it.

"Having an important part of your past erased is trivial?" she countered, raising her own eyebrow before jumping to her feet and swooping her belongings up into a careless bundle. "I wouldn't say that. Besides, you didn't regenerate that first time on Gallifrey, did you?" The Doctor shook his head. "All right, then, what's the prob? Just zip on over to see you after you 'retired' but before you regenerated, and ask yourself what the deal is. Maybe this memory thing just happened recently," she added encouragingly. "If it did, then your first you should be able to help this you." A sudden thought struck her. "Or maybe you should talk to Susan, see what she remembers."

The Doctor came to his feet, absently handing Ace one of her socks. "Perhaps that isn't such a bad idea," he murmured, turning and heading up the path. Ace drew up next to him. "I'll have to think about it." In spite of the warning tone of his voice, Ace could tell by his eyes that he'd already made up his mind. She felt her heart speed up, although she tried not to show her excitement. Finally, something to do, something to break the boredom. A new adventure.

The two of them entered the TARDIS and shut the door behind them. Minutes later, the time machine was gone, leaving no trace that anyone had ever been there except a flattened spot in the middle of a clearing, and a lone sneaker, lying forlornly on the bank of the river where it had been forgotten.

Author's Note: This is an alternate universe story to a certain extent, as it offers an alternative origin for Susan Foreman-Campbell than the novels do (and, as you can see from above, kills off a certain character who in the novels becomes the President of Gallifrey). I do not generally make use of the novels as I have read very few of them, and so consider only the TV series (and the Fox Dr. Who movie featuring the 8th Doctor) as canon. Although the ending of the story appears to place this even more firmly into an alternate universe, just remember that things are not always what they seem in the Whoniverse. Enjoy!