"I don't know where you expected to get spare parts for this on Earth," the Doctor said, peering into the smoking device. "They're centuries away from this sort of technology, you know."
"You usually seem to manage," the Master said. "I thought those wretched UNIT people might've come up with something..."
"Well, they haven't," said the Doctor, and he sat back and scowled at the Master, who supposed that he did deserve a scowl or two this time around. He hadn't meant to build a faulty vortex manipulator that had taken out a perfectly innocent library, two grocery stores, and a UNIT platoon before he'd gotten it contained, but there the thing was; he had been planning only to test it on Earth and then hold some more valuable planet hostage with it, which was now quite out of the question with it so unstable. Even contained, the manipulator wasn't safe - damned machine could go off any moment, and then... The consequences hardly bore thinking about.
The Doctor saved him from that line of thought by saying, "I suppose it's all very well for you, since you've still got a working TARDIS, but you might have left me out of it. I can't fix the blasted thing without proper equipment and I can't get off Earth; a clear victory for you, I should think."
"My dear Doctor! Not in the least," the Master said, and then rubbed his temples. He had not meant to say that, at least not so openly; the manipulator's failure was getting to him. It was unfortunately true, however, that he could not bring himself to count wiping the Doctor from existence as a victory, and particularly not when he hadn't meant to involve the Doctor in this scheme at all. "I mean to say," he said, "that was not my intention - if you can't fix the manipulator, I shall take it off Earth and dispose of it, that's all." If he was extraordinarily careful with it and only moved in space, he might be able to get it somewhere he could implode it without too much damage to the universe...
"Don't talk rubbish," said the Doctor, who didn't need the risks of moving a faulty manipulator in a TARDIS spelled out for him, even if he could be remarkably dense in other ways. "No - I'll take another look, have the Brigadier send some of my equipment up - we can work out some sort of fix, I'm sure. At least," he added sharply, "if you'll quit standing about and help me."
"Naturally," the Master said, and went to phone the Brigadier.
Had she been present, Miss Grant probably would have called them both ungrateful; the Master thought they had simply gotten too used to keeping each other alive to bother with courtesies every time.