Why Earth?
It was a question he'd been asked, oh, so many times. And he'd answered it. He had a hundred answers, ranging from the intellectually sublime right up to the downright ridiculous.
It had a nice climate.
He liked the people.
It was the only place in the universe he could buy edible ball bearings.
Humanity was fascinating.
There was an abnormal variety in species.
Humans had such an impact on the universe, and he was still trying to figure out why.
They were always getting into trouble.
Accident.
It was cheering to see so much life.
The planet was in a good spot, spatially, for astrological phenomena to be observed.
They made good jelly babies.
And occasionally, when he'd had it up to here with the questions, he'd just reply with "because I feel like it!"
And all of those reasons were true.
Absolutely, uncompromisingly true.
Except…
…whenever he gave one of those reasons, he knew that however true it may be, it was still lying by omission.
Because in his soul he knew the reason he was drawn back to that one planet; and he knew that it had nothing, whatsoever to do with humanity.
"Theta, will you come outside? You've been working all day."
Koschei landed rather heavily in the chair next to his best friend, whose eyes barely flickered from the screen in front of him.
"In a minute."
Koschei sighed loudly and impatiently.
"You've been saying that since the beginning of the day-cycle," he said despairingly. "It's not like you to work so hard. What are you reading that's so interesting, anyway?"
He leant in over Theta's shoulder, trying to see, only getting a glimpse before the other boy turned it off – but a glimpse was enough.
"Earth." Koschei's voice was flat and blank. "You're obsessed with that stupid planet."
"It's not stupid!" Theta snapped, his temper flaring. "You're always reading stuff, studying things, and I don't ever complain! But when I decide that I want to learn something –"
"What more can you possibly have to learn?" Koschei retorted angrily. "You spend half your life pining over that rock, you must've picked up something by now!"
Theta's eyes narrowed.
"You're just jealous," he said quietly, his voice tight with fury, "you just want me to be hanging on your every word, and you can't stand the idea that I might find something more interesting to do."
"That's not true!"
There was genuine hurt in Koschei's voice, and when Theta looked it had reached his eyes, too. Koschei looked away.
"You know I only study so hard because father expects it of me," he said softly. "I have to."
Theta watched his best friend, his anger dissipating like water in cupped hands.
"I just –" Koschei's breath stuttered a little, and Theta knew how hard it was, how hard it always was for Koschei to explain how he felt " – I just missed you. Okay? We haven't been together for a while, and I miss you." His voice got quieter towards the end of his speech, but the sincerity in his tone was unmistakeable. Theta reached out and placed his hand on Koschei's.
"I know," he said. "I'm sorry."
Their eyes met, and Theta felt that familiar thrill of making contact with someone who was his absolute equal, his perfect match. He smiled.
"Let's go out on by the water," he said. "We could both do with some air."
Koschei nodded, but as they left together he stopped. Theta looked back at him, curiously.
"What is it?"
Koschei took a breath in and let it out slowly. Then he looked up at Theta.
"You should bring that file out," he said, nodding to the screen Theta had been using. Theta looked pleased with the idea, but bit his lip.
"Are you sure you don't mind?" he asked. Koschei gave a half-smile.
"I'd rather see you happy," he said.
Earth.
Theta's pet project, Koschei had called it. It had pulled them apart on more than one occasion, been the source of an argument more than once. But it had been his trademark, his label – Theta who studied Earth. And Koschei had forgiven his little quirk.
But it had never been forgotten.
Yes, the Earth was beautiful. Yes, its people were fascinating. Yes, its food was good, and humans really were always getting into trouble. But that wasn't why he was always drawn back there. He was drawn back there because he knew, he knew so well that if there was one place in the universe that Koschei would know to look for him, it was Earth. It was always Earth.
Earth that Theta – the Doctor – protected from every threat he saw. Earth that Koschei almost always attacked first. Of course, sometimes they met elsewhere; they were both travelling, they both could end up anywhere. But they both knew that Earth was where Theta would always end up – and where Koschei would always look for him. They both knew that Earth was the one place they could be certain to find each other.
Why Earth?
The Doctor fended off each question with jokes and wry comments and obscure science, but always knew that he returned for Koschei. Sweet, beautiful, lost Koschei; in the guise of the twisted, brilliant Master perhaps, but still Koschei underneath it all.
His Koschei.