Title: Experimental Subjects
Fandom: Doctor Who
Rating: PG, if only for very silly drug use.
Summary: In which Theta and Koschei should have known better than to ask Ushas for help with mind-altering substances.
Author's notes: Many thanks to UseTheForceEm and Ciryatúre for their encouragement and support, for their extensive contributions to the characterisations of Koschei and Theta, and also for inventing the blue-skinned humanoids of Nefevin II and their very interesting social customs.
X-Post: A Teaspoon and an Open Mind
Disclaimer: No affiliation with Doctor Who or the BBC. No money is being made from this.

"It's science, don't you know?" Theta said. "Well. Anthropology."

"Which is not a science," Ushas shot back. "My answer is still no."

Koschei rolled his eyes at Theta as their friend returned her attention to the centrifuge. "I told you that argument wouldn't wash," he said.

"Fine. You try. See if yours works any better."

Koschei grinned. Leaving Theta to deal with their centrifuge and the class experiment that they were allegedly working on, he sloped over to Ushas and leaned insolently against her lab table. "Have I mentioned how fetching that colour is on you, Ushas?"

"Sod off, Koschei."

"Hear me out, oh light of my eyes. I know Theta's proposal fills your lovely head with nothing but contempt, but the fact is, I do agree with his request, albeit not for the same reasons."

She didn't answer at once, being too involved with checking the pipettes and loading them into the centrifuge. After she felt she'd let Koschei dangle for a suitable length of time, she started the centrifuge and finally turned to him. "You have until this thing finishes spinning to make your case. Go."

"Well, quite simply, it'll be fun."

"As if you two didn't have enough to distract you from—"

"I don't simply mean for us. For you. Darling, sweet Ushas, I know you. Do you think I've forgotten the way you manipulated the pollen compounds on those pansies last year? How radiant you were from the sense of accomplishment?" He pouted slightly. "Really, I thought it'd be a warm day on Io when you'd fail to jump at any excuse at all to play games with a plant's chemical compounds."

"Bloody cheek," she snapped. "Thinking I'll aid and abet more of your mischief after that debacle last week with the harrier beetles. You really are mad, Koschei."

Something flashed in his eyes then, but she was bowed over her instruments and didn't see it. And there wasn't any of it in his voice when he continued smoothly, "Mad only for you, dearest. Come on now, please? It'll be a challenge. And besides, I know you're going to finish the latest xenobiology assignment two weeks early; surely you don't want to be bored for all that time."

The centrifuge whirred to a halt and Ushas sighed. She looked up at Koschei with the faintest hint of a smirk. "Let me think about it."

"That's all I ask, my love." With exaggerated courtesy, he took her hand, bowed over it, and kissed it. He wasn't at all surprised when he got clipped on the shin with the toe of her boot (rather hard) for his trouble, but it was worth it.

"She's going to castrate you one of these days, you know," Theta said as Koschei rejoined him. "Well?"

Koschei chuckled, rubbing his hands together gleefully. "Oh, we're in, we're in. She claims she's got to think about it, but you know her."

"How you get round her like that, I'll never know."

"You just don't understand women, Theta. Now shove over so we can finish this—oh."

"You didn't think I was just going to sit here and waste all that time, did you? C'mon, you can help me write up the results."

The blue-skinned humanoids of Nefevin II had many peculiar customs in their Golden and Silver Ages, most of which were regarded with considerable fascinated disgust by the young acolytes of the Prydonian Academy. One of the least disturbing practices was the lunar vision ceremony, which involved the smoking of certain dried herbs to induce a state of mellowness, euphoria, and general one-ness with the universe.

When they looked back on it later, Theta was convinced that the whole thing was Koschei's idea, and Koschei was equally vehement that none of it would have ever happened without Theta's eternal, demented curiosity about the habits and rituals of lesser species. Ushas didn't care whose idea it was; the important part was that she had achieved the stated goal of boosting the active chemicals in the Nefevinian herbs to the point where they had an actual chance of affecting the Gallifreyan physiology—and what's more, had done so without attracting the attention of any of their professors.

Some three weeks after the conversation over her lab table, Ushas knocked on Theta and Koschei's door and presented them with a small jar of dried plant matter. "You'll keep me informed about the results, I hope," she said.

"Of course we—wait, you're not going to join us?" Koschei frowned.

"Wish I could, but I've got a time-critical distillation that I really need to be getting back to. Bad timing. Another time, though. Enjoy!" A little finger-wave, and she was off.

That this should have been some kind of red flag was so obvious in hindsight that neither Theta nor Koschei ever mentioned that part of the business again.

"Koschei?"

"What?"

"I can't feel my face."

"Thought that was supposed to be normal."

"'S not. Least I don't think so."

"Huh."

Silence.

"Theta?"

"Hmm?"

"I can't feel ... anything."

"What d'you mean?"

"I mean nothing. Poke me."

"What?"

"Not like that, you fool. With your finger."

Silence again.

"Well?"

"I just did. 'S funny, when I did it, it was like my hand wasn't, y'know. Wasn't there."

Koschei slapped a hand to his forehead. It was partly an attempt to check in on his nerve endings, and partly a gesture of sheer exasperation. The sensation was curious; both hand and head registered that an impact had occured, but it was as if both were buried in masses of cotton-wool. "You know better than I do, Theta; what's this stuff do again?"

"Euphoria. Happiness. Pleasant feelings towards one's fellow-beings. All that." Theta had slumped down onto the floor and was staring up at the ceiling with a tiny little frown. "Pretty sure there's nothing in it about numbness."

"Unexpected side effect due to Gallifreyan physiology? Or—"

Theta turned his head and the two looked at each other in horror. Or at least as much horror as they could muster on their benumbed faces.

"Harrier beetles," Koschei said.

"Got to hand it to her," Theta mused. "Carries a grudge like no one in the galaxy."

"Going to kill her."

"I'll help."

Yet another profound silence.

"Soon as we can move, she's dead."

"Completely."