It's all AU.

Hunting down an alternate future self to persuade him from going a bloody rampage or starting some other cracked scheme - probably one of the most unique things the Master would ever experience. This place was enough to do anyone's head in.

It was certainly doing the Doctor's head in. It was one thing for the Doctor to wish he could change his own personal timeline. It was another to actually contemplate it. And the Doctor had actually been contemplating it, when he spoke to Adric, the Master could tell. That bit of madness creeping out in his own Doctor - that shook the Master.

But that moment had passed and the Doctor seemed simply grim and resolved now. The Master, likewise, let none of his worries show, projecting self-assurance as they patrolled the town looking for any sign of trouble. Or indestructible Jacks they could enlist to help them. It would be good to have a someone who couldn't stay dead on their side, in case laying down the law did not go peaceably. He had to admit to himself he was beginning to like the idea of having Jack around.