The 456 were a set point in time that the Doctor couldn't interfere with, as much as he may want to. It had to happen and then the Earth would move on, as it always did, until the next emergency.
That didn't mean he couldn't at least save one person. Just one. That couldn't hurt things too badly. And if he was saving one person it might as well be the one important to his friend. Even if Jack wouldn't know that Ianto Jones had been saved.
So, at the last second, as everyone was passing out, the Doctor made his appearance, showing up just in time to drag Ianto's unconscious body into the TARDIS and far away from the toxic gasses infiltrating his system, getting to work on removing said toxins as soon as they were in the TARDIS and on their way to somewhere else.
It was a few hours before Ianto actually woke up, slowly blinking his eyes open to look around himself.
"Ah, you're awake then! That's good! I'm –"
"The Doctor. Yes, I figured as much." Ianto interrupted. He didn't seem all that surprised to see where he was. Working in Torchwood one couldn't be too surprised to find themselves in the TARDIS if they ignored the fact that the Doctor had a track record of not getting along with Torchwood. "And just where have you been, Doctor? The Earth needed your help." He added, trying to keep any resentment he'd had for the Doctor since Jack had left with him, that had only grown with each day they dealt with the 456 alone, out of his voice. Or rather, if he was being honest, resentment he'd had since the Doctor hadn't stopped the cybermen soon enough to save Lisa, but he blamed himself more for that than he did the Doctor.
The Doctor went into a long winded explanation, complete with wild hand gestures and 3D glasses, that all boiled down to 'Fixed point in time. I'm sorry, I'm so sorry. It really couldn't be helped. The humans do win in the end though.' "So, Ianto Jones, all of space and time at your fingertips! Where do you want to go first?" The time lord ended with a grin.
"I want to see Jack." Ianto said without hesitation.
The Doctor hesitated at that, grin faltering and a slightly pained look crossing his face.
"Don't you give me that look. Don't you dare. I know he's alive. It would take a bit more than some contaminated air to put him down. I've seen him bounce back from far worse." Ianto said, sounding more like he was trying to convince himself that Jack was okay. Because surely if he could actually be killed by the 456 he would have been the one the Doctor would save. But the look that had crossed across the Doctor's face had worried him despite that knowledge.
"No, it's not that. He's fine. He does have a remarkable ability to bounce back from death. It's just. . . well, I can't exactly take you back to your time to see him. Everyone in your time thinks you are dead. A tragic martyr who died defending the Earth. You get a memorial in Cardiff and everything. But because you are dead in your time, I can't take you there. Anywhere else though."
"Then don't take me back to my time. We can go far enough ahead that everyone's forgotten me, but I know he'll still be alive, and I need to see him. Even if he doesn't remember me, I just need to see him. I don't even have to talk to him if that's too much. I'm not expecting anything to come of seeing him, I just need to." And he really wasn't expecting anything. He was sure if they went far enough ahead Jack wouldn't even recognize him. Despite what he had said one time, to an immortal man who had new adventures and lovers and friends to look forward to how could Ianto not just be a blip in time to him? The word 'Don't.' in response to his confession ran through his mind to remind him that he shouldn't expect anything from this. Besides, even if Jack did recognize him, standing next to the Doctor what did he matter? The Doctor was the one Jack truly loved. The Doctor and Rose Tyler, but she didn't appear to be with the Doctor at the moment. "You can take me wherever or whenever you want afterwards, but please just let me see him this one time if I'm not going to be able to go back to my time to see him anymore." Closure was the word his mind supplied him with to inform him of exactly why he felt like he needed to see Jack, even if only for a second.
The Doctor gave him an unreadable look for a long moment before he nodded. "Let's see where we can find him then. Jack Harkness isn't an easy man to find once Torchwood is destroyed. He's got to keep people from noticing the whole immortal thing after all." He said, starting to fiddle with things on the TARDIS console. "Found him! How do you feel about an Earth colony six hundred years in the future?" He said, spinning on his heel to face Ianto.
"If that's where he is then I feel like that's where we should be." Ianto replied.
"Then hold on tight to something." The Doctor pulled down a lever and suddenly the sound of the TARDIS started up, and Ianto took his advice to hold onto something.
When they landed Ianto was out the door in a matter of seconds, the Doctor following behind him.
Ianto's eyes found Jack quickly, standing chatting with someone on the other side of a busy street, filled with humans and aliens alike. However, the sound of the TARDIS seemed to have caught his attention because his head turned in their direction so quickly Ianto felt like he was getting whiplash just looking at the gesture. And then his eyes were locked on Ianto and he started making his way across the street faster than he should be able to with the number of beings walking it.
"We should go. He'll want to talk to you, I'm sure, and you didn't want people to see me." Ianto said to the Doctor.
The Doctor was giving him the same look he had been before deciding to take him here, and Ianto still couldn't figure it out. "You're probably right, but you know, I haven't seen Jack in a while, might as well say hi." Calculating. That's what it was. The Doctor was planning something.
Ianto was about to question the time lord's sanity , but then Jack was in front of him, gripping Ianto's chin to turn his face away from the Doctor so that they were making direct eye contact, Jack's eyes intently searching his.
"Doctor, what did you do?" Jack asked quietly, not taking his eyes off of Ianto.
"Brought you a friend. He was very intent on seeing you when I picked him up." The Doctor replied casually with a shrug of his shoulders.
"You're really here? You're really Ianto Jones?" Jack asked him.
Ianto tried to nod, but Jack's hand was still holding his chin in place. "Yes. It's really me. A mad man in a blue box who can't keep straight if I should be seen or not rescued me." Ianto replied, offering a small smile before he found his face pressed against Jack's chest as he was pulled into a bone crushing hug with Jack's head resting on top of his.
"Ianto Jones, you somehow never cease to amaze me." Jack murmured into Ianto's hair.
The Doctor took this as his cue to leave, quietly slipping back into the TARDIS, unnoticed with a small smile on his face. "Guess I'm in the market for a new companion. All of time and space at his fingertips and he picks one man. Jack is lucky to have met someone like Ianto Jones." The Doctor said to the TARDIS as he started setting her for a new time and place.
He was sure Ianto would be fine with Jack. And really, what was oneperson being saved in the grand scheme of things? This far in the future he was sure it was fine to have Ianto and Jack around each other.