"They leave...” he pauses, swallowing the lump that's risen in his throat. “Because they should, or they find someone else, and some of them... some of them forget me. I suppose in the end..." His discomfort isn't at telling Jackson one of his deepest secrets, his problem is he knows by admitting it, it makes it much more real. "They break my heart."
Eventually he agrees to have Christmas dinner with them and it breaks his hearts even more because when he looks at Rosetta all he can see is Rose and Martha and Donna all bundled into one. And he looks at Jackson and sees the bravery of Jack and the determination of the other-him and the compassion of Mickey. And this is almost like the Christmas dinner he had after defeating the Sycorax.
He knows he shouldn't be pitying himself. Jackson lost his wife to the Cybermen. At least all his companions are alive, even if he can never see some of them again.
But really, they all die in the end anyway.
The sound of the Tardis materialising startles Jack out of his thoughts.
"Back so soon? Have you broken something?" Jack grins over his shoulder at the Doctor exiting the Tardis. "You wouldn't come see me unless you wanted me to do something? You're the Doctor, what could little old me do?" Jack knows his tone is a little bit bitter but he can't help it. "The great Doctor needing my help?"
"Yeah, I do." The Doctor doesn't say anything else. He's come to stand next to Jack, and Jack's staring at him but he just looks down over the city. "I never really apologised, did I? The old me left you there alone in the dark and I never apologised." He grows almost silent at the end.
"Doctor, I -" Jack starts to speak but the Doctor cuts him off.
"I'm sorry," he speaks louder this time, despite the desire he has to curl up in the heart of the Tardis.
"I know." Jack reaches out and lays a hand on the Doctor's shoulder. "I always knew, because you're always sorry this time 'round."
They are silent for a moment, staring at the city below, and the Doctor realises how much he misses London. Because it had started to feel like home.
"They all die in the end, while we live on." The Doctor sighs as he finally speaks the truth that's been haunting him for so long now. "They leave and I never see them again and one die they'll die."
"No, Doctor, they don't." Jack's voice is strong and unwavering.
The Doctor finally looks at him and Jack sees the unshed tears in his eyes. "What?" The Doctor raises an eyebrow, but only slightly, as if the effort is too much for him.
"Rose Tyler is gone from this universe, she officially died at the Battle of Canary Wharf, but in so many millions of years she'll be standing on a satellite platform watching the Earth be destroyed. And years before that she's standing on a similar platform, glowing, and bringing me back to life," Jack smiles comfortingly at the Doctor, "Martha Jones lives in London currently, eventually in linear time she'll die, but years in the future she's stuck in traffic on New Earth."
The Doctor looks at him and smiles sadly.
"Donna Noble can't remember your face, but somewhere in the stars you're staring at hers is stuck to the body of a souped-up library monitor," Jack winks at the Doctor's suprised expression. "Donna and I had some time to chat."
"Jack?" He says it like a question.
"Wait, let me finish. You make us immortal Doctor, every companion you take with you. Because no matter what happens we'll always be somewhere, a hundred years in the past or a thousand years in the future and we'll be there forever."
Jack turns the Doctor to face him and grins in a way that practically seeps warmth into the Doctor.
"It's part of your magic, Doctor. You take us and you make us special and brilliant and clever and beautiful, and you make us forever." Jack sighs and pulls the Doctor into a loose hug.
Suddenly the hug isn't loose anymore as the Doctor brings himself closer to Jack. He's pushing himself into Jack like he could bury himself under Jack's skin and hide there forever.
Jack holds the Doctor as rough sobs wrack his body. Jack's shock is overridden by his desire to help.
"Doctor," Jack starts speaking but he doesn't know what to say so he gently coaxes up the Doctor's face so he can look at him.
They stay still for what seems like an eternity. The Doctor's eyes are dry but his body stills shudders with an occasional sob.
"Doctor -" Jack tries to find something to say but he is cut short by the Doctor's lips pressed against his.
It isn't a tender kiss, it's a kiss because of pain and loss and because Jack knows the Doctor wants to feel something other than hurt.
As they kiss Jack remembers something Ianto told him once when Jack had been teasing him for crying, 'we cry when we are overwhelmed' he had said, 'not when we're sad or happy or tired or lonely or relieved, we cry when we have so much emotion in our hearts that we don't know what to do with it'.
Jack knew the Doctor never cried, so he did this instead. And Jack's heart broke for him because how much pain must he be in that even two hearts are overwhelmed.
The Doctor breaks the kiss off abrubtly and stares, in a way that is almost a glare, at Jack. "They leave... Because they should, or they find someone else, and some of them... some of them forget me. I suppose in the end... they break my heart." The Doctor says them quietly and Jack understands that these words aren't new.
The Doctor starts to leave without even acknowledging Jack, but as he nears the Tardis door Jack finds his voice.
"Doctor," Jack starts for what he knows will be the final time tonight.
The Doctor pauses, and Jack knows he's making that split second decision whether or not to wait, he does.
"Forever." Jack says the word like a secret, like a question, like a promise and like a command.
"Forever," says the Doctor, and it sounds like resignation, and a curse.
The night is still, broken only by the sound of the universe as the Tardis disappears.