So this is what it felt like.
Jack Harkness (he never thought of himself as "Captain Jack", the rank being one he had no legitimate claim to, though he was happy enough to wear the title as a glamorous badge) felt something break inside him as the TARDIS completed its dematerialisation sequence.
What was there to break? He'd long since given up thinking there was a heart in there. Until recently of course.
And now: no point shouting or raging or weeping or looking for a communication set. The TARDIS could be centuries away, milennia even. Anywhere, anywhen. And the chances of his path crossing the Doctor's again were ridiculously tiny.
"Aw hell," he said aloud.
There was no-one to hear of course, no-one to respond. He was marooned on an empty communication station above an Earth that was presumably still being torn apart by the…
"Wait a second," he looked around. "maybe two seconds, tops."
No Doctor. No Rose. No people.
Jack touched his chest thoughtfully at the point where the Dalek gun had seared into him. Tender, but nothing more. He had been dead, he was sure of that. From the moment the slide of his pistol had clicked open on an empty magazine he had been a dead man. And those damned cyborg war-machines had taken their time, enjoying the moment; don't try to tell Jack Harkness they had no emotions. They enjoyed their work.
And then they had finished the job and killed him.
But now he was alive. He walked slowly along the length of Floor 500's control room, trailing his fingers absent-mindedly along the consoles that now showed nothing but meaningless self-diagnostic alerts ("Hull Breach: OB-Plat BB4Y" one flashed repetitively) and garbled text. The trailing cables that had once neural-jacked the Controller into the station output hung from the abandoned control point like flayed snakeskins. Even the Controller was gone. Only Jack remained.
So this is what it felt like.
Usually Jack was on the other side of this particular divide. He was the great rogue Time-Agent, a cross-contextual scammer with a ship full of stolen technology, an answer for every situation and an eye for available beauty. "Nice to meet you (insert name)" and a practised smile. Then he would get what he wanted which usually included but was not limited to a certain amount of pleasure.
And then he would leave. Timeslip away without a word, without an emotional scene. And sometime shortly afterward that certain (insert name) would realise what had happened and stand looking at the blank space and wonder: Is this a mistake. Is he coming back?
He'd actually enjoyed the feeling of doing that sometimes. That hardfaced bitch Jeminda Maramahana who kept the records in the Hofex Collective in the late 28th century. He'd slipped away with her diamonds, the passwords to every account in the Collective, and the sure and certain knowledge that she'd take her anger out on every faceless bureaucrat in her section for months afterward.
Or Eleanor Greel, pretty little Eleanor all safe and sound in Daddy's fortress in the heart of Uluru. Swept off her feet by the dashing Time Agent and so keen to provide the security codes that finally brought Magnus down. Then one last kiss in payment for her betrayal and Harkness had gone for good, leaving her confused and hopeless.
And now it had happened to him.
Maybe this was Hell, he thought to himself. Maybe that's how this deal works. You die, you wake up again, and all the crap you've pulled on other people gets pulled right back at you. Alone and abandoned surrounded by piles of ashy Daleks and a heartful (no, not heart) headful of memories and regrets.
Jack found himself at the door to Archive 6 and touched the palmlok to open the door. The TARDIS had been in here earlier that day and an irrational conviction arose in him that the ridiculous blue box would be back.
Nothing. Just a couple of discarded component-boxes and a screwed up page from an out of date celebrity magazine. The Face of Boe, he learned as he glanced down, was threatening legal action against the Ranoratharipest Adepts who had infringed his trademarked appearance by worshipping him as a deity and started carving Shrine-Idols with his likeness on them. No TARDIS in here. He closed the door and walked away.
"This isn't fair," he said. How many others had said that because of him? But this was different, he told himself. He was changing, he had changed. Hell, he'd changed more in the last few weeks than in the rest of his life put together. He had found himself surprised on a daily basis by the depth of the feelings that were growing for his travelling companions. Feelings so deep that when it came time to make the final decisions he did not hesitate. Even if he could have abandoned them to the Daleks he would not have done so. Even if it cost him his own life. He rubbed at his chest again: It had.
But that was the point. If this was Hell then it was unjust. He had changed, he had started to be able to love, really love, to put aside his life as a philandering vagabond and to enjoy the wider universe that he had come to see as being composed of … well… people. As opposed to suckers, victims, or sex-objects. If this was his Hell then something was wrong. He didn't deserve this anymore.
He sank down in despair, his back against the console-bank, staring at nothing.
Maybe he was still a fake, maybe his new found feelings were fake too. He'd heard the Doctor a few days ago telling Rose again that the TARDIS was telepathic. They'd been arguing after delivering the Margaret/Blon egg back to her home planet.
"It gets inside your head," the Doctor had said, "at that moment, the TARDIS knew more about Margaret than she knew herself, and it knew what to do. It changed her into what she needed to be."
"Yeah, you said," Rose had replied, "for a new start and everything. It just seems a bit, I don't know, like an easy way out."
"Easy is sometimes good," the Doctor had answered with a tone that suggested the conversation was over. "Easy is not always a bad thing. Anyway it may not be that much of an easy option. Nappy training for her species can take about a decade. Imagine that."
Jack smiled weakly at the recollection of the casual banter that had passed the time inside the TARDIS. No longer alone, starting to connect. But maybe that was just the TARDIS working on him, getting inside his head and translating more than languages. Maybe it had been translating him into a different person. Maybe it was too little too late.
No. He didn't believe that. If his feelings were fake then this wouldn't be so bad, wouldn't hurt like this. Alone on the Gamestation, nothing to do but wander around the empty game-sets and find as much liquor as possible to numb his mind into happy oblivion.
"Well done housemates," he said bitterly, "you've completed this week's task, dying, successfully. Your reward is a lonely eternity of scavenging from tv studios on a ruined spacestation above a dying Earth."
With no one to pretend to, the despair he felt twisted his handsome features into an ugly mask of misery. The brief glimpse he had had of a better life made this abandonment all the worse. The tiny sip of real love, given and received, made an eternity of arid thirst more horrible than he could bear.
He buried his head between his hands, hunched over on the floor, and wept for some time, deciding.
When he finally looked up, his eyes were fixed on the jury-rigged detonator of the Delta wave device. The Doctor had been working on this, the ultimate weapon. It would generate a pulse that would fry the brain of every organic entity within transmission range. From what Jack had seen on the displays the Earth was probably toast anyway. The Dalek fleet was almost certainly still around. Even if this wasn't a one-man Hell. Even assuming the Doctor had finished his work. It was the best choice he could see.
What was there to lose. He stood unsteadily and walked to the side of the detonator.
"Courage, and shuffle the cards," he quoted to himself. That was from Lola Montez (19th century Earth, nice legs, bad temper, Imperial jewellry).
He was about to reach for the detonator when an unfamiliar voice startled him.
"That won't work you know, wouldn't bother trying it."
Jack turned round quickly. The newcomer was a youngish man, wearing a loose white shirt at least a size too big for him and tight trousers. Jack slipped his habitual mask back on and grinned.
"Who says it won't work? A friend of mine put this together and he doesn't make mistakes. Captain Jack Harkness by the way." He held out his hand.
"Oh he makes mistakes all the time Jack, all the bloody time, he's just very good at covering them up," the newcomer didn't shake Jack's hand, instead he handed him the inert end of a thick power cable. "And it won't work because I've just unplugged it." The young man grinned back. "Come on Jack, I thought you Time Agents were sharper than this."
Just beyond the smiling newcomer Jack saw movement in the shadows. A woman, a shape he recognised. A big smile beneath hopeful eyes.
"Nice to meet you, Captain Jack Harkness," quipped the Doctor embracing his friend, making just enough room for Rose to dash forward and join in, the pair of them smothering him in love, genuine love.
So this is what it felt like.