Post-COE. This is part of my Intertwining Lives Series.
He'd put on a good front for Gwen and Rhys, but once Jack was off the planet he stopped pretending that things would get better.
He spent three weeks on the freighter before he lost himself in the press of bodies on a drab space port. The crew of the ship shrugged it off, no skin off their nose if a hitchhiker wasn't aboard when they left.
He drifted. Hopped a ride on another ship and took it as far as it went. Stowed away on a military vessel and got executed for it. Woke up and swiped a junker from the scrap heap.
Fixing it up gave him something to think about. But thinking about one thing lead to thinking about others. He didn't want to think about anything. When she was space-worthy, he started running again.
It was five months after leaving Gwen and Rhys on the top of that hill that the Doctor caught up with him.
He turned a corner, walking back to his ship with his latest supplies, and there it was, a big blue box with the Doctor, oh, so casually, leaning against the TARDIS's frame.
"Hello, Jack," the Doctor said.
Jack just stared at him.
The Doctor opened the door of the TARDIS and looked questioningly at Jack.
Jack cocked his head for a moment, but then shook it in denial.
The Doctor nodded; however, instead of leaving like Jack expected, he approached. He held out his hand, "Give me your vortex manipulator."
That finally got a verbal response out of Jack. "What?"
The Doctor sighed. "I know what it is you want to do right now Jack, and I'm in no position to tell you not to. But I'm going to set it so if, when, you are ready, you can contact me. I told you before the invitation to travel with me is an open one, but you can call even if you just want a night's sleep in your old room."
Jack shook his head, not in denial this time, but in disbelief. "Why? How could you... Why would you...?" Jack let the questions trail off.
The Doctor didn't answer, but instead reached into his pocket and pulled out his sonic screwdriver.
Jack didn't let himself think too hard on the questions he had left hanging, or on what the answers might be. He took off the wristband and handed it to the Doctor.
The Doctor handed it back to him a minute later.
"Thanks." There wasn't any real emotion behind the word.
The Doctor nodded anyway and turned to go. "Oh, one more thing." The Doctor faced him again and pulled something out of his pocket. "I believe this is yours." He held his hand out and waited for Jack to lift his own to receive whatever it was.
A TARDIS key dropped into his hand.
Jack was still staring at it when the TARDIS faded from view.