It's all AU.

Jack went back to his TARDIS, to make sure she was OK, and to add the information he'd discovered.

He found the right tree, and was about to unlock the ship, when someone he hadn't seen for hundreds of years walked out the shadows.

"She's mine," Jack told him. "Working chameleon circuit, too."

D'athe reared back a moment as he stepped through the door, his ears flattening against his head, and his feet scrabbling uselessly for a door that had vanished. He was investigating the strange and chemically smells of a lab, not some town street!

Spinning in a circle a moment, he studied the scene around him. Mystical, wierdy doorway gone, check. Modern paved street that made his claws hurt, check. Buildings that humans griped when he walked on them instead of the street, check. Still somewhere familiarish, but not where he'd been before. Excellent!

He let out a small warble of glee, scrabbling up the building he was next to, launching himself over the edge onto the roof to land with a small grunt before spinning in place, looking out over the edge at the town laid out below him again. So interesting, so different, and brought to him by a wierdy doorway.

This is FABULOUS! Better than a mad scientist, any day! They're all chemically smells and glass exploding in my face, anyway. Though usually they don't have wierdy doorways where there doorway is, so I shall have to investigate that one a little more when I get back.

He looked around the roof, spotting a human male, and bounded over, tilting his head, ears pricked up in greeting.

Hello! You wouldn't happen to be the one who made the wierdy doorway, would you?

Brant had shown Jack to the bar, and he was sat at a table, drinking...something. It was bright green, and tasted vaguely like whisky.

And then someone he hadn't seen for five hundred years took the seat next to him.

Following some very pleasurable activities, Jack kissed the Doctor and Martha goodbye, listened for the Doctor's TARDIS's dematerialisation noise, and sent his own TARDIS into the Vortex. Now that he could, he planned to go to 2000, and watch Rose for a while.

Then his ship unexpectedly lurched. "Whoa, Emma, sweetheart. You been picking up bad habits from the old girl?" Jack pressed levers and buttons, trying to get her under control. Minutes later, they landed, rather heavily.

And in a park, near some trees, according to the monitor.

Apparently, that was the only where he was going to get.

When was completely out of the question.

"Better go investigate, then," Jack said, leaving his ship. He locked her up, watched the chameleon circuit kick in, assuming the form of an oak tree, and walked towards the park's exit.