The city is always the same. Unsalvageable rusted-out husks of ancient vehicles, massive concrete structures overgrown and crumbling. And of course, the omnipresent machine threat. Which is why it's important to always stay alert for any tiny change in the environment.
Such as the man, strolling through the ruins and whistling the same four notes over and over again.
"Scanning. Subject is not a machine life-form. Neither is it human."
He waves at her.
"But then... it's not an alien."
"No. Subject does not match database records. Proposal: Unit 2B should approach the subject and determine its origin and intent."
"Yeah." She starts walking over, moving quickly.
He eyes her swords and slips a hand into his pocket, but continues to grin at her.
She stops a short distance away.
"Who are you?"
"I'm the Master. Who are you?"
"2B. Master of what?"
"Myself, time, everything, depends on how I'm feeling."
"Where did you come from?"
"Just now? Nowhere. Originally? Gallifrey."
"Searching. No references to 'Gallifrey' found."
"Are you an alien?"
"I am. What are you?"
"Who built you?"
"We fight the alien machines to take back Earth for the humans."
"Not my alien machines, just so we're clear."
"Mm." It's not clear if she believes him.
"Seriously, why would I want this planet? There are much nicer ones."
"I just told you I came from Gallifrey, keep up."
"Then... how did you get here?"