He gets there just in time to see a man open a door in the side of an oak tree. 

Sadde hides behind a tree, and watches.

The man steps inside and the door shuts behind him.

Just before it does, Sadde gets a glimpse of a cavernous room.

He zips towards the tree and knocks.

The man leans back out, "Yes?"

"Why are you in a tree and why is it bigger on the inside."

The man leans on the door frame and looks Sadde over.

"It's not a tree. It's a spaceship."

"Why does your spaceship look like a tree."

"Most people don't knock on trees, but everyone wants to see the spaceship."

"Why is there a spaceship here at all? And why do you look human if you're an alien?"

"My ancestors weren't very creative. Why do you look human?"

"Evolutionary pressures over several million years and a fair amount of luck. You're designed?"

"Edited. Besides, this form isn't as rare as humans seem to think. I know of at least three species who could walk around here and not raise a single eyebrow."

"Which of course raises the question of why."

"Maybe the universe ran out of ideas."

"I'm pretty sure that's not how evolution works!"

The Master rolls his eyes and heads back inside the TARDIS, leaving the door open.

If that's not an invitation he doesn't know what is. He follows.

He enters into an enormous wood paneled dome. In the center, there's a bank of instruments surrounding a giant tube that's full of a slowly pulsing amber. 

The Master goes to one of the wood panels, which opens, and pulls out a long in metal rod which has a circle mounted on one end. He points it at Sadde.

And now Sadde is behind the Master.

"Do be careful where you point things."

"Subject identified, TARDIS," the rod chirps. 

"You're fast! What are you?"

"What are you?"

The Master points the rod at himself.

It chirps, "Subject identified, Time Lord."

"- is that the name of your position or a title or...?"