A/N: This fic is a gift for one of my LJ friends, who gave me this prompt: "The Eleventh Doctor is on his Farewell Tour (set just after Closing Time). He thought Craig was the last person on his list, but he is not. Who else would he see? And how would the meeting go?"

Hope you enjoy!

A Memorable Occasion

Part I

The explosion painted the sky azure.

Martha was moving at once, doing damage control.

"Monitor whatever telephone calls you can, find out how many people saw it and if it's enough to be taken seriously. The last thing we want is for the press to be getting ahold of this story. Colin, how many were stationed in that area?"

"Four, ma'am," he replied.

Martha Jones raced around the pile of disused tech to look at his computer screen. They were holed up in an unmarked truck in a deserted lot, a few blocks away from the explosion. Jennifer and Harold, also in the truck, were alternating between typing furiously and reporting to their superiors. Martha's phone buzzed with an incoming call, but the moment she saw who it was, she canceled it.

"I'm going out there," she said, double checking for her handgun.

"Ma'am, I really must protest—"

Martha silenced him with a look.

Jennifer jumped up from her seat before any of them could say anything else, shoving several papers into Martha's hands. "These are the readings we were able to take of the site just now. Radiation levels, toxicity, a list of trace substances we were able to get from the scans that we just took of the area. Sorry, it's not much, I'll be working on a more detailed analysis later."

"Thanks, Jen." Martha didn't have time to smile. "Right you lot, Harold's in charge. Keep on a lookout for any similar spikes around here, but don't go looking for them."

The three of them saluted sharply, which nearly had Martha rolling her eyes, but she was already halfway out the back door to the truck, jumping down to the pavement. She barely felt any exertion as she sprinted the short distance of a few blocks to where the explosion had originated. It was one of their watch points, so Martha knew that it couldn't be a coincidence. Jennifer had been right about the transmissions in this area: something else was going on.

Only a lone dog-walker saw the woman dressed in black military fatigues race down the street, but he only stared for a moment before continuing on his sojourn.

Her phone buzzed again. Unable to take the time to cancel the call, Martha ignored it again. She would deal with the voicemails later.

There was no noticeable change in the explosion radius; as it had earlier, the street contained a block of condominiums that sat sleepily in their places, the windows dark due to the late hour. Unlike earlier, however, there was no sign of any of the UNIT personnel that had surreptitiously taken up positions at various spots. Martha checked each one for clues, starting with the ancient oak tree and ending with the mailbox that had the Union Jack on it.

Apart from one of the red berets, she found nothing.

Martha moved until her back was against one of the trees before pulling out the papers that Jen had given her. No alarming spikes in radiation, no lethal elements in the atmosphere— apart from a brief increase in what appeared to be pure energy, there was nothing to indicate that there had even been an explosion at all.

Martha mentally categorized what she knew of alien technology. As far as she could remember, none of the species she had encountered thus far were capable of producing explosions without some kind of aftereffect. Whoever this lot were, they were good.

For the third time that night, her phone buzzed in her pocket.

Still keeping one eye on her surroundings, she checked the caller ID. Jennifer.

"Yes?"

"The energy spike was the effect, not the cause."

"What?"

Jennifer let out a huff. Martha knew what that meant.

"Try to explain in English, at least."

"Yes, ma'am." The sarcasm was easy to detect. "Look, basically what happened was that the explosion was the effect, not the cause. I've managed to back-trace the chemical composition in the air with the scanners we set up, going through each millisecond of the explosion to see if anything changes. You'll have noticed that there was no particular indication of any use of lethal weaponry, right?"

"I noticed," said Martha impatiently. Her arm jerked at sudden movement out of the corner of her eye, but it was only a raccoon.

"Well, moments before the big blue… thing— sorry, there's really no technical term for it— a really faint signal was sent out. What's weird about it is that it behaved like a living thing, or some kind of search-and-destroy algorithm."

Martha forced herself to take a deep breath. "And it found what it was looking for?"

"Yes ma'am." Jennifer lowered her voice. "It hunted down our four soldiers and, to put it simply, converted matter into energy."

This nearly rendered Martha speechless, but she wasn't in charge of this particular missions for nothing. "The energy spikes—"

"Yeah."

Martha closed her eyes.

"Ready the truck for departure," she said in a low voice. "We're heading back to HQ for the night."

"Understood, ma'am."

Martha snapped her phone shut. Before she made a move to leave the completely innocent row of condominiums, she flipped through the papers one last time to look at the chart of energy readings. She needed to stare at four particular hikes in the data for a good five minutes before she was finally able to move.

Stetson.

Jack blinked.

The man wasn't half-bad looking, either, but his dress sense left something to be desired. That coat with that hat? Either would have looked fine on their own, but the combination of the two made him question what sensibility there was in allowing this man to dress on his own.

"Are those what you call important questions?" exclaimed the man. He looked young and he sounded young. "What about, 'Should I or should I not be making sure that the space under my bed isn't occupied by Sandleberg Newts?' Or, 'Is the neighbor's cat really a cat, or is it really an assassin'— not that you could tell the difference. Personally, I think that all cats have it out for us. They're just biding their time. Visit one of the hospitals in New New York, you'll see what I mean."

"Am I dead?" Jack blurted out.

"Well, you were." The man paused, shifting a bit. "Probably. I think? I'm not sure if there's a difference between being dead or just being unconscious for you anymore. You get to wake up from both."

The man was wearing a bowtie, as well. Jack added that to his mental list of 'things that should not be worn in combination with one another'.

"How did I even get here?" he groaned, rolling over onto his side and finding himself face-to-face with blue. "Oh."

Upon rolling back over, other surroundings began to take shape as well. The shimmering light bouncing off the walls of London's underground catacombs, caused by a combination of the harvest moon and a canal that snaked its way through the darkness. Jack dimly recalled tracking his quarry through here when an impact with his head made everything go dark.

"She really has it out for me, doesn't she?" Jack asked, looking back at the TARDIS.

The Doctor shrugged. "Debatable, I s'pose. She's a bit cross with me at the moment as well, so it could very well not be you. Sorry about crashing into you. I was aiming for ancient China; I thought I might be able to visit Confucius for a few days. Did you know that Confucius was actually an alien? Anyway, Jack Harkness! As much of a fixed point as ever!"

"Thanks for the reminder," Jack replied, standing and dusting his coat off. "Not a bad look, Doc, but I stand by what I said before about the way you dress."

"Oi! There is nothing wrong with the way I dress!"

Jack gave him a patronizing pat on the shoulder before he searched for any signs of the thing he had been chasing. "You didn't happen to see a humanoid-but-not-human being run through here after you landed, did you?"

"Nope."

It seemed that the Doctor had become a professional at appearing to be unconcerned, but the minute Jack turned his back he heard the whirring of the sonic. He made to slip his own scanner out of his coat, but discovered his pocket was vacant.

"Damn," he muttered.

"Trace signs of a—"

When the Doctor abruptly stopped speaking, Jack winced.

He was expecting something like a half-hearted glare when he turned around to face his old friend. The exasperated look that said, 'What are you doing now, Jack?' The eyes that he came face-to-face with now were dark green, accusing, and ancient.

He was well aware of the Time Lords' ability to reduce their age rate. But the Doctor's previous incarnation had never really struck Jack as old— not in the way that this one did, now.

Jack raised his hands in a gesture of surrender, trying to ignore the ice that was crawling up his spine. "I'm just doing Martha a favor." He paused. "You, uh, remember Martha, right?"

In only a moment the Doctor's expression cleared. "Martha Jones!" he exclaimed happily, bouncing on the balls of his feet. "How could I forget Martha Jones, the woman who walked the Earth? How is she? Splendid as ever, I suspect."

"Doing well, from what she told me." In truth, Martha hadn't provided many details about her personal life in her short phone conversation with Jack. She'd sounded distracted.

"Right. Good." The Doctor pirouetted to face the canal again. "Your quarry swam for it, by the way. So! You, Jack Harkness, are trying to hunt down a Lvaaina, for some reason that Martha failed to disclose to you. Since no Lvaaina has made any attempt to leave their home system in their official published history ever (information courtesy of a friend of mine at Luna University, I should add), I can't imagine what they might be doing here. Or," and here his eyes changed again, "what you might want with them. Lvaaina are probably the most peaceful creatures in all of existence. Absolutely no evidence of warfare of any kind."

Jack could only shrug helplessly. "I only know what Martha told me. She gave me explicit instructions not to hurt it, but…"

"Something's clearly wrong," the Doctor finished.

"Martha told me that she's set up a temporary headquarters somewhere in west London."

"Then that's where we're headed!" exclaimed the Doctor. "Come along, Po— Jack."

Jack watched curiously as the Doctor made a peculiar face, as though he'd eaten something distasteful and felt the immediate need to spit it back out again. He began muttering to himself as he pushed open the TARDIS door, but the only thing Jack was able to catch was, "…not the same…"

The Doctor wasn't the only one to have regenerated, it would seem. Jack nearly stopped in his tracks at the unfamiliar interior, but decided that he liked it after taking a moment to absorb the soft, but warm lighting it provided. There was an artfulness, or maybe an elegance, to it that the older, more antiquated desktop had lacked. He did raise an eyebrow at some of the unusual contraptions on the console (a typewriter?), but he was quickly distracted by the whirring noise as the Doctor and his ship took off.

Jack grinned. At least the sound hadn't changed.

"No fellow travelers?" he inquired.

Clearly the Doctor wasn't expecting the question, because he almost tripped over himself while doing another spin.

"What?" he asked, once he'd regained his footing. Jack eyed the way he twisted his hands together. "No, no. Well, yes— good friends of mine, the Ponds— but, well. They've settled down now. Bought them a house and everything. And a car! Rory's favorite car. He wasn't expecting that one, let me tell you."

"You usually find someone new."

The Doctor moved around to the other side of the console, using the column to block Jack's view of him.

"I dunno. Might be different this time around. Here we are! Scanner says we ought to be parked right outside Martha's spot."

Jack meant to ask more, but the Doctor was off like a rocket, bounding out the door without waiting for Jack. He sighed, resigning himself to the fact that this Doctor would be even more difficult to get a straight answer out of than the last, before following.

It was still early evening; Jack checked his mental clock, and decided that the Doctor probably hadn't accidentally jumped ahead a year. The sun bled orange across the horizon. It suited the run down warehouse that served as Martha's headquarters, the light reflecting off the metal that the now-peeling paint was beginning to expose. Already the Doctor was arguing with one of the beret-capped soldiers, probably because none of them would dare believe that the illustrious Doctor would wear something as ridiculous as a bowtie.

He sauntered over, flashing a charming smile at the guard. "Captain Jack Harkness. Martha Jones is probably waiting for me inside."

The guard seemed oblivious to his flirtatious tone, choosing instead to stare at him sullenly before he stepped aside to let them through.

It could hardly be called a buzz of activity. The warehouse had only one— albeit large— room, in which several workstations had been set up for the scientists to carry out their contributions to the mission. There weren't many soldiers present, apart from the guard that he and the Doctor had encountered. One or two, waiting for orders, and Jack guessed that there were probably a few more stationed around the perimeter.

Martha herself was slumped over a steel table that had several maps on it. Jack guessed that she was trying to triangulate the position of the other Lvaaina, with minimal success. He noticed the Doctor falter at the sight of her out of the corner of his eye, but he himself didn't pause as he made his way over to her.

"Martha Jones," he said, saluting with a grin.

Her slight jump was succeeded by a bright smile at the sight of him. "Jack," she greeted him, scoffing at his salute and embracing him instead. "I'm sorry for throwing this on you all of a sudden. How are you?"

"I've been making do." Jack had been exploring ancient assassin cults for the past 50 years, but Martha didn't need to know that. "And it isn't any trouble, Martha. Really. You look awful, by the way."

"Work." Martha gestured to where the similarly haggard science officers sat at their computers, hacking away at keyboards. "You know how it is. I can't afford any breaks, not with something on this scale."

"You also shouldn't have to work on something of this scale by yourself," he told her. "Why haven't UNIT sent any reinforcements if it's getting to be serious? And where's Mickey Mouse?"

"He's at home."

Jack stared at her.

Martha stared right back at him, an unreadable expression on her face. There were the beginnings of lines underneath her eyes— barely noticeable, but there. She didn't look underfed, at the very least, but well-rested was another matter entirely.

"A couple of nights ago, before I contacted you," Martha began, looking back down at her maps. "There was a sudden explosion here: Charrington Road. It didn't cause any physical damage at all, and the only readings we were able to get were four energy spikes and a search-and-destroy signal that was sent out moments before the explosion." She stopped, looking at her hands. "I had four soldiers stationed there. They were gone by the time I arrived on the scene."

Jack tensed. However peace-loving the Doctor claimed the Lvaaina to be, it was clear that they weren't too keen on maintaining that reputation.

"We've spent the past two days trying to find the origin of the signal," Martha continued. "Whatever they did, though, they've covered their tracks well. The trail's getting colder every hour we fail to find them."

"You don't know that they haven't left yet," Jack reasoned.

"Why wouldn't they? I doubt they would want us to find them—"

"Look, they're probably hiding something in this area, and they saw the soldiers you posted as a threat."

To the side, someone coughed.

Jack forced himself to stop for a moment, surprised to discover that he'd nearly forgotten that the Doctor was there. He looked at the Time Lord, who stood a few feet away, fidgeting with his hands again. His eyes darted between Martha and Jack, as though debating which of the two he ought to speak to first.

"I forgot to mention," Jack added, "that I brought along a surprise."

This seemed to break the Doctor out of his dilemma. "You brought—? I'll have you know, Jack, that the TARDIS was actually being nice for once. Next time maybe I ought to actually charge you a fee!"

Jack lifted up his arm, allowing the sleeve of his coat to slide down and reveal the vortex manipulator affixed to his wrist. "I could've gotten here easily, Doc."

"Doesn't count," he muttered.

"Doctor?"

For the first time since their arrival, Martha looked like she was really alive. The shock had brought some of the light back to her eyes.

"Is it really…? I mean, it makes sense. That look you gave me and Mickey, and I just knew— but of course you got younger. And of course your dress sense got worse."

The Doctor spluttered wordlessly. Jack, on the other hand, mumbled, "Finally, someone else."

Martha was quick to pull the alien into a hug. The Doctor flailed a bit before he seemed to sag forward slightly, closing his eyes and letting out a soft sigh into her shoulder. Something about the vulnerability of his gesture— something his previous incarnation would never have shown— made Jack's heart ache a bit. Whereas before, when the Doctor found out that Jack was looking for a Lvaaina, he had looked old, he now looked like a child.

When the two broke apart, Martha appraised him. "Not taking care of yourself again, are you?"

The Doctor laughed quietly. "When do I, Martha Jones?"

Jack smiled to himself, letting the two of them catch up while he looked over the maps himself. There were scribbles and crossed out lines in red pen, notes in the smallest of white spaces and an array of what he knew to be different attempts to find the location of the signal.

He looked for the street that Martha had mentioned, and saw what neighborhood it was in.

The dots connected.