"That's impossible," Gwen said. "Tattoos don't just fade like—" She turned to Jack, then whirled away and stared hard at the ceiling. "Jack, your towel."

Toshiko blushed and looked away, and Owen coughed pointedly. Jack glanced down and re-wrapped the towel he'd thrown loosely around his waist before climbing out of the bunker. Once they'd realized the tattoo was missing, Jack had abandoned his shower plans and called the team in to investigate, but he hadn't bothered to dress again. The tucked end of the towel kept coming loose, letting the fabric slide down below the level of decency.

"You could have taken the time to put your trousers back on," Ianto pointed out. "A missing tattoo isn't exactly a seconds-count emergency."

"Didn't exactly have to call us all back in for it, either," Owen muttered. "I hadn't even gotten home yet."

Jack ignored the comment. "I'd just have to take them off for the scans anyway." He leaned over Owen's shoulder to look at his screen, his bare shoulder nearly brushing the doctor's ear. "So what did you find? Any residual… anything?"

Owen scowled and leaned away from the naked torso beside him. "Nothing. Not even a trace of subcutaneous ink. How long has it been gone?"

"I can't be certain. It happened sometime since…" He glanced at Ianto. "When's the last time you stared at my naked ass?"

The silence that followed was beyond awkward, and Ianto felt his face growing hot. "Um. Not since… before you left with the Doctor, I think."

Owen scratched his chin. "So it could have happened any time in the last six months."

"Fourteen," Ianto corrected, then remembered that the rest of the team didn't know about Jack's extended travel. He shot Jack an apologetic look, but Jack waved it aside.

"Ianto's right. I was gone with the Doctor for over a year. A lot… happened to me, so I suppose the tattoo might have been affected then."

Gwen shook her head. "But tattoo ink wouldn't vanish in a year. It can fade a little over time, but that takes years. There ought to be some trace of it."

Toshiko gave Gwen an appraising look. "You seem to know a lot about tattoos. Do you have more than just the one bee?"

Gwen flushed. "Please don't ask. I was young and stupid. It was a phase."

Toshiko grinned. "That sounds like a story for later."

Owen tapped through his test results again, then frowned up at Jack. "You're sure it was a tattoo, right? Not a scar or something that could have healed when you died and came back?"

Jack shook his head. "I've had it for years. Decades. If it were going to reset when I died, it would have happened long before now."

"Where did you get it done?"

Jack looked faintly sheepish. "I'm… not sure. I was kinda drunk at the time. Just woke up with it."

Gwen's jaw dropped. "You got yourself a tramp stamp while drunk?"

Owen snorted. "How pissed do you have to be to not remember getting a tattoo?"

"Isn't it a little unprofessional to tattoo someone who is intoxicated?" Toshiko put in.

Jack rolled his eyes. "It was back in the seventies, okay? A lot of people were on a lot of drugs. I'm probably just lucky it was on my arse and not somewhere more visible."

Toshiko's head snapped up. "What year?"

"What?"

"You said it was the seventies. What year?"

Jack hesitated—only an instant, but Ianto saw it. "It was the fifth of August, 1976."

Toshiko raised her eyebrows. "You don't remember getting the tattoo, but you're certain of the date?"

"I'm certain."

Gwen frowned. "How can you be sure, if you were so drunk?"

Jack's expression shuttered. "It was… someone's birthday."

"I see," Gwen laughed. "Must have been some birthday party, then. Too much partying?"

"Just the opposite. I wanted to…" Jack shook his head. "I ended up in a big fight with someone I'd been close to. I was angry and upset, so I went and deliberately got hammered on alien liquor." He crossed his arms. "It wasn't my proudest moment, but it's what happened."

"August, 1976," Toshiko murmured, leaning over Owen's other shoulder to use his keyboard. "I'd just turned a year old. Your tattoo was almost as old as me, Jack!"

Ianto shivered. Of course he knew, objectively, that Jack had lived in Cardiff for well over a century, but despite Jack's offhand comments about his adventures with Queen Victoria or Neville Chamberlain, he'd never really thought of Jack as that much older than the rest of the team. But when the time was counted by the lifespans of people Ianto actually knew, Jack's advanced age suddenly seemed more real.

Sudden pressure closed Ianto's throat. No wonder there had been such a gulf between them, when their life experiences were so different. How could he have ever thought they were meant for each other? Jack had to be six times Ianto's age—possibly even more, since Jack refused to reveal his true age. He'd seemed sincere enough when he'd asked Ianto on a date, but how could Ianto ever be anything more than a diversion for Jack, when he was only a child by comparison? Once more Ianto felt a twinge of loss for the signum he'd never known, the person who would have matched him in both age and affection…

Before the misery could seize him again, Ianto shook himself and consciously squelched the self-pity. His signum had gone, just like Lisa had gone, and there was nothing to be gained by continuing to mope about something he would never have. He had to focus on the future. On the present. On his life right in this moment, and the possibilities it presented.

On Jack—whose towel was beginning to slip again. Ianto cleared his throat and motioned to Jack, who hitched the fabric higher on his hips.

Toshiko hummed softly as she scrolled through files on the computer. "It was a long shot, but I don't see anything major for that date in the rift records."

Jack rolled his eyes. "You really think aliens came through the rift and stamped a Torchwood logo on my ass?"

"Well, aliens somehow managed to brand every child on the planet with a coded symbol, so I wouldn't put it out of the realm of possibility." She stopped and blinked suddenly. "Wait, that date was after the meteor shower. I wonder…" She turned and jogged up the steps to her own workstation. "Give me ten minutes," she called over her shoulder.

Owen glanced up at Jack, still mostly naked beside him. "As the attending physician, might I suggest you use that ten minutes putting on some pants?"

Ten minutes later, Jack—still not showered, but now at least clad in trousers and a t-shirt—joined Toshiko at her workstation. "What've you got?"

Toshiko set down her soldering iron and brandished a scanner, now festooned with some extra wires and a dangling circuit board. "Sorry, I didn't have time to make it pretty. Ianto, Gwen, would you mind showing me your arms? No, the one that had your birthmark." She ran the scanner over the place where each of their marks had been, then examined the readouts on her terminal. "Good, it's working. Now, Jack, turn around and pull down your trousers."

Jack flashed a salacious grin. "If I had a penny for every time I heard that…"

"You'd deflate the pound, with so much money leaving circulation," Ianto finished.

Toshiko scanned the area where Jack's tattoo had been, then worked with the data on her screen. After a moment, she turned back to Jack. "Well, I have good news. Your tattoo did not vanish."

Jack glanced up from buckling his belt. "You mean it's still there? Invisible, or something?"

"I mean it was never a tattoo to begin with. Look at this." She pointed to the display. "I was able to detect the remains of the nanites that had made up Gwen and Ianto's birthmarks. They're gradually dispersing, but the organic components are still concentrated in the area where their marks were. And the site of your tattoo is showing the exact same percentages." She turned back to Jack and spread her hands. "It wasn't a tattoo. It was a SoulMatch birthmark."

Ianto's heart stuttered.

Jack frowned. "How is that possible? I wasn't even born on this planet."

"No, but you were exposed to the same seeding enzymes as all the unborn children that year. And you do have a tendency to come back from the dead. Maybe the nanites responded to that somehow."

Owen had joined the group while Toshiko was explaining. "You said you don't remember much of the night you got drunk?"

"No, I just blacked out and woke up the next morning. I didn't even realize I had the tattoo—or whatever it was—until someone pointed it out a few days later. I just assumed I must have gotten it while I was drunk."

"Could you have drunk yourself to death that night? Alcohol poisoning? Accident?"

Jack shook his head. "I always know if I've died. Coming back is… it feels different. And if my body had reset, the hangover wouldn't have been nearly as bad as it was." He grimaced with the memory, but then his expression changed. "Wait a minute. I think I did die not long after that. There was a big case… It would be in the records. Ianto?"

Ianto, standing off to one side, didn't answer until Jack called his name again. "Er, sorry. What did you need?"

"Get me the mission reports for the two weeks following the fifth of August, 1976."

"Right. Back in a mo." He felt Jack's eyes boring into him as he retreated to another terminal and pulled up scans of the archived files. It took several attempts; his hands were trembling too much to type. "Got them. Sending them to your screen now."

Ianto hung back from Toshiko's station, fists shoved deep in his pockets, as Jack perused the reports on her display. "Here it is," Jack said after a few minutes. "I remember this. I was caught in a boiler explosion on the eighth. That one definitely killed me; nearly blew one of my legs off, and burned sixty percent of my body. I was limping for a week. Took me days to regrow the skin…" He broke off and exchanged a glance with Toshiko. "Oh. Does that mean…?"

"I think we have to assume it does." Toshiko confirmed her theory with a look at Owen, who nodded his agreement. "You were exposed to the nanites shortly before growing a lot of new tissue. Evidently they established themselves in your body then, and gave you a birthmark just like all the newborns."

"So Jack was the only person over thirty who had a birthmark," mused Gwen. "See, Jack? You weren't too old!"

"Well, it's no wonder they wanted him in the program," muttered Owen. "Their goal was maximum procreation, after all…"

Ianto couldn't maintain his composure any longer. He left the others laughing and hurried back to Jack's office, where he slumped against the desk and tried to still his pounding heart. His breath came in gasps, and he tugged at his collar, feeling strangled. After so much time, and so much longing, and so much worry… He scrubbed damp palms against his trousers.

A few minutes later Jack entered the office, shutting the door quietly behind him. "I've sent the others home, since it turns out it's not a crisis after all." He stopped beside Ianto and touched his shoulder. "What's going on? You looked upset out there. And I'm guessing it's not just because we had to postpone our date," he added, forcibly lightening his tone.

It took Ianto a moment to find his voice. "Your mark," he managed after a few false starts. "It was the Torchwood T."

Jack nodded. "Weird, isn't it? That's why I assumed it was a tattoo. I never imagined a birthmark would look…" His eyes widened in realization, then went to Ianto's wrist.

Ianto closed his eyes. "They were the same."

Jack took a deep breath. "You're sure?"

"You remember when I first told you they'd found a match for me? The reason they didn't put me in contact with my signum then was because they couldn't locate them."

"What does that mean?"

"I heard Dr. Peters say they knew who it was, but their system couldn't pinpoint that person's location anywhere on the planet." Ianto opened his eyes and met Jack's gaze. "That was two months ago."

Jack counted back. "When I was with the Doctor. On another planet."

Ianto nodded.

"I see." Jack swallowed. "So… I guess that means we're compatible."

"More than that." Ianto spoke slowly, letting the words sink in. "It means I've finally found my signum." He reached for Jack's hand, tentatively lacing their fingers together. "And so have you."

A look of wonder dawned on Jack's face. "Until a few minutes ago, I didn't even know I had one."

A little flutter of panic passed through Ianto's stomach. "Disappointed?"

"Just the opposite. It's kinda nice." Jack digested the concept for a moment, then smiled. "I can see the appeal in knowing for certain." He put his arms around Ianto. "Not that I was ever in doubt."

Tears stung Ianto's eyes, and he pressed his forehead against Jack's neck. It felt so right, as though this were where he had been headed all along. This was where he belonged, and somehow, through everything, he had always sensed it. "I wanted it to be you, Jack. All the time I was searching, I just wanted it to be you."

Jack pulled Ianto close, holding him as though they had never been apart. "To tell you the truth," he murmured against Ianto's ear, "so did I."

The confession shot warmth through his core. Unable to contain his ardor a moment longer, Ianto crushed his lips to Jack's in a searing, long-overdue kiss, which Jack returned with equal passion. For a time, the rest of the world fell away, and there was only their connection. Their souls, truly reaching each other for the first time.

A few minutes later, when he had caught his breath and rediscovered gravity, Ianto gave a thoughtful hum against Jack's cheekbone. "You know, I'm glad the marks are gone."

Jack roused himself from nuzzling Ianto's throat. "Oh? I thought you were pretty invested in the whole soulmate thing."

"Too invested, I think. In the end, the marks only got in the way. I mean, as you said, it's nice to have confirmation that we're—well, maybe 'meant to be' isn't the exact phrase, but… right for each other? Compatible?" He shrugged. "But I only feel that way because I was already in love with you when I found out you were my signum."

Jack's eyebrows shot up. "You're… in love with me?"

Ianto felt the warm flush creep up his neck, but it was no use denying the obvious. "Keep up, Jack," he chuckled, pulling him in for another kiss.

Jack reciprocated enthusiastically, then pulled back to search Ianto's face. "You don't think it would have worked the other way around?"

"You mean, if we'd found the marks first?" Ianto shook his head. "Can you imagine, when I first came here, if I'd just walked up to you and introduced myself as your soulmate?"

"I probably would have panicked and actually run you over with the SUV that time," Jack admitted. "You're right, it's better this way."

Ianto nodded. "It'll take some adjustment, but in the end, I think people will be happier making their own choices. Knowing it's what they want. Not being told whom they're supposed to be with, and then trying to figure out how to make it work."

Jack traced a thumb across Ianto's cheek. "And you still would have chosen me? Even without a mark?"

"I did choose you without a mark, Jack. I chose you when I thought you just had a regrettable tattoo. But I would have chosen you no matter what was on your arse." Ianto smiled coyly, and his hands dropped to Jack's waist. "Speaking of which, I think it's about time you had nothing on your arse."

Jack laughed. "A man after my own heart."

"I've been after your heart for months."

"You've got it now." Jack moved closer. "Along with the rest of my body, if you're interested."

"I'll take ownership right after you shower." Ianto kissed him lightly. "You still smell like a garbage fire."

Jack scowled. "There's no need to get personal."

"Oh, getting personal is the end goal. But shower first."

Jack leaned in, his lips brushing Ianto's ear. "Join me?" he murmured.

Ianto made a show of thinking it over. "We still haven't had our date yet."

"We can always go out for a late supper."

Ianto chuckled. "All right. But I will need to borrow some clothes."

"Trust me," Jack grinned, "you won't need them for a while."

Ianto rolled his eyes. "Is it always going to be like this with you? A constant stream of innuendos, come-ons, and double entendres?"

"Hey, you're the one who started it."

"Never said I didn't. I just want to make sure you know what I expect of you."

Jack laughed and tipped his forehead against Ianto's. "I keep thinking I know what to expect of you, but you still surprise me, Ianto Jones."

"I try my best."

Jack stayed there for a moment, his smile softening. One hand came up to cradle Ianto's face. "I would have chosen you, too," he whispered. "You know that, don't you?"

Ianto leaned into his touch, savoring the affection. "I know, Jack."

"Good." Jack kissed his forehead, then stepped back and took his hands to lead him toward the bunker ladder. The blinding smile returned to light his face. "Now come on. There's a tiny shower downstairs waiting for two grown men to cram into it."

"I'm glad you specified 'grown.' I was starting to question my maturity."

"Probably due to the conversation we've just been having." Jack waggled his eyebrows.

Ianto answered that with an eyeroll. "Proving that whatever the age difference between us, we're at least equally immature."

Jack traced his thumb over the inside of Ianto's wrist, where his birthmark had been. "I guess that's why we're a perfect match."

"One of many, many reasons," Ianto agreed. He stepped close and kissed Jack, slowly and tenderly and full of love. "Let's go start a list."

Fin.

ADVERTISEMENT: Stay tuned for the sequel, Marked! Well, more of a fluff epilogue, really. But it will be up very soon!

Author's Note: So here's another box checked on my fanfic bingo card! Soulmate AUs are the candy of the fanfiction world: Sweet and indulgent, bite-sized, and frequently with little substance beyond what it says on the tin. And like delicious candy, people can't get enough of them. Sometimes you just need that sugar rush (especially in a fandom like Torchwood's, where the subject matter is often heavy and must be countered with a regular diet of happy feels).

It should come as no surprise that dark chocolate is my indulgence of choice—the really dark kind that takes forever to melt on your tongue. So for my candy story, instead of writing a sweet, fluffy soulmate AU that resolves in one chapter, I went for something a little darker and more complex. I wanted to combine the soulmate concept with the world of Torchwood canon, which is the diametric opposite of sweet and fluffy (and usually involves aliens). As with many of my stories, the plot developed into something bigger than I'd planned, and jumped from an estimated 20K words to 74K. I hope it was worthwhile, and that my dark chocolate was not too bitter for readers who were expecting something with more sugar content!

Acknowledgements: Thank you SO MUCH to everyone who followed the story and commented, especially those of you on AO3 who provided your thoughts or theories as I posted each new chapter! I appreciate each and every response, and in some cases, your comments actually prompted me to alter bits of the story or write additional scenes that hadn't been in my original "final" version. All told, I added around 6,000 words to the story between the time I started posting and the time I finished, including one entire additional chapter. (See? The more you comment, the more story you get to read!)

This story probably would not exist without gmariam, who stirred up my muse during chats about her canon-following soulmate fic Animoré and also put up with weeks (months) of me dragging my feet and complaining about scenes I wasn't happy with. And a tip of the hat also goes to Alicewantsjam, whose comment on Animoré got me thinking about soulmate registries and how they would work. (See? The more you comment, the more you inspire other people to write stories for you to read!) :)

Chapter note: Since it didn't fit neatly into this chapter's narrative, I ended up cutting it from the final draft, but I know someone will wonder about the significance of the date Jack got drunk. August 5, 1976 was Melissa Moretti's first birthday. Lucia Moretti didn't put Melissa into hiding until 1977, but at some point, she forbade Jack from seeing his daughter, which he naturally would have wanted to do on her birthday. You can extrapolate the reason for the fight and why Jack was so upset on that particular night.

Thank you for reading!