"Changeling venom," the doctor announced, throwing a glance over his shoulder to the sleeping body on the bed, "we'll have to wait for it to naturally be disposed of by her system, that'll take a couple of weeks given how much was injected in her. It's not the typical variant, but there's no doubt about what it is. We could synthesize an antidote, but we would need venom from the changeling that bit her in the first place to do that." He began to walk towards the exit.
Rarity looked between him and Twilight's sleeping body. "Is there..." she tried, words getting stuck in her throat.
The doctor turned towards her. "Yes? Did you say something?" he asked, adjusting his glasses with a hoof.
"I... No, it was nothing," Rarity said, defeatedly lowering her head.
The doctor turned and walked away. "Visiting hours end in thirty minutes, please leave the room by then," he reminded the two while going through the exit.
The sound of the door closing echoed in the room, and Rarity sighed, looking at the floor. A wing tentatively reached her back, and she looked at her side. "I'm sorry you had to be dragged into this, dear. Thank you for helping me with carrying Twilight. And with finding this place, I would have probably gotten lost, shocked as I was."
The pegasus smiled at her. "Oh, don't worry. She's a princess, after all, I was just doing my job." He stroked her neck with his feathers. "I'm terribly sorry about this happening to your partner, I hope she'll get better soon."
Rarity half-smiled, looking back at the floor with a bitter expression on her face. "It's not too big of a problem. At least, it wouldn't be, Twilight being out of commission for a while, if it was just that. The problem is that it's happening now, and now's really not the time for something like that." She wistfully looked up at Twilight.
The pegasus sighed and did the same. "I'm Smoke Screen, by the way. I already know your name's Rarity, no need for introductions there."
"Well, nice to meet you, Smoke Screen," Rarity replied, a little more cheerfulness in her tone.
Smoke Screen adjusted in his seat, moving his grey tail out of the way from below him. "So, Rarity, what brings you and Princess Twilight here to Canterlot? Is it a simple visit for pleasure's sake or are there orders from above?"
"A mission," Rarity replied, "the Cutie Map sent us here and... Wait, if you didn't know about it, then when you said 'partner' earlier... Oh gosh, did you mean... Me and Twilight..." Rarity's face coloured red.
Smoke Screen looked at her, a little taken aback. "Oh, sorry, it's just... Rumours circulate here among members of the royal staff. Is it something I shouldn't know, or is it just-well, incorrect?"
Rarity regained some of her composure. "I-Well-It's not... We're not together, like that. I mean, I like her, but not-Like her, you know? I'm not into mares, that's all."
It was now Smoke's Screen's turn to blush. "Oh I'm-Sorry, about that... Well, I mean-" he blushed even harder "-I'm not sorry about that, you know what I meant, it's not like I'd be sorry to know you weren't into stallions and I-Eh-" He bit his tongue to stop his rush of words, and if anypony who didn't know him had looked at his face at that moment they wouldn't have known it should have been pale custard and not blood red.
Rarity chuckled, and moved a strand of grey mane out of the way of Smoke's face.
The stallion looked at the floor, occasionally throwing a furtive glance up at Rarity. "So, you were saying about your mission?" he tried.
"Oh, yes. I believe you know about the Cutie Map, correct?"
Smoke Screen nodded. "I've heard of it, yes. I don't know much about the specifics, but I think I get the general idea."
"Good. As I was saying, the Map sent us here in Canterlot, so there's supposed to be a friendship problem of some kind for us to solve. It was already a pretty bad time for something like this, given what Twilight thinks will happen in about a week, and then we couldn't find anything once we actually got here, which just made things worse." Rarity looked once more at the alicorn's body. "Twilight being poisoned like this right now is just the worst possible thing!" she dramatically added, leaning back in her chair and posing with a hoof on her forehead.
"Can I..." Smoke bit his lower lip. "Can I ask what's supposed to happen next week?"
Rarity brought a hoof up to her mouth. "Oh my, you haven't heard?"
Smoke Screen shook his head.
Rarity furtively looked around. "King Sombra is supposed to come back," she said in a low tone. "At least, according to Twilight's calculations."
Smoke Screen gasped. "King So-" His voice was muffled by Rarity holding up a hoof to his mouth.
"Shh," the unicorn said, "it's supposed to be a secret only for the princesses and the Royal Guard. We don't want somepony finding out about it and then creating mass hysteria by spreading the rumour around the population, do we?"
Smoke Screen gulped and nodded.
Rarity removed her hoof.
The pegasus leaned forward. "King Sombra is coming back?" he asked in a whisper.
Rarity nodded. "At least, that's what Twilight thinks will happen, and she's usually right about this sort of things."
Smoke Screen looked around the room, then leaned a little closer. "Do you think whoever poisoned Twilight did it on purpose so she wouldn't be able to stop him when he comes back?"
Rarity frowned in thought. "That's a possibility, yes. But who would want something like that?"
"Perhaps the two things are unrelated," Smoke admitted. "Princess Twilight does have many enemies, after all. Still, this might be quite the problem. Whichever the case, we should try to find the culprit, don't you think?"
"We should," Rarity agreed. "Oh, but what can I do? How am I supposed to search the whole castle for both the friendship problem and the one who poisoned Twilight? I can barely get around here, and Celestia's guards have already failed at one of those things, and last I heard they were failing at the second too. This is just terrible!"
"Well..." Smoke Screen offered her a hoof. "I can help, if you want. I know my way around the castle pretty well, and this seems like a serious issue. What do you say?"
Rarity looked at his hoof, surprised. "I mean... Isn't this going to interfere with your job?"
Smoke Screen gave a brief laugh and a small shake of his head. "My job is to serve the princess, and"- he looked at Twilight -"she looks like a princess to me. Plus, I don't think her Giant Spiderosity is going to notice the lack of one single member of her staff." He smiled. "And even if she does, I think this is more important. And, well, likely more entertaining as well." His voice dropped to a whisper. "Don't let it get out that I said this, but working under Celestia is boring. I have to stand around doing nothing all day, and the rare times I have to do something it usually involves looking at inventory lists at best. Count me in on this thing."
Rarity hesitated one moment longer, looking between him and his hoof, then she smiled and offered her own.
Smoke smiled back, and they shook hooves. "Do you already have plans for where to start?" he asked, drawing back his leg.
Rarity put her hoof to her mouth in thought. "Well, we need Twilight to wake up if we want to stand a chance against Sombra, and we need her awake for the friendship problem as well. So first things first, we should find out who poisoned her."
"Sounds like a sound plan to me," Smoke replied.
Rarity sighed. "If only I had any idea of where we should actually start searching." She looked up. "Any ideas?"
Smoke munched on his lower lip. "I... Okay, here's my train of thought. Changeling venom can usually knock somepony out in a matter of seconds. The version that hit Twilight is different though, it's clearly slower. Well, unless you're the changeling, but we can't really work under that assumption."
Rarity drew back for a moment at the words, a quizzical and somewhat offended look in her eyes.
"Here's the thing though, it's still changeling venom. It can't be that different. It probably works in a matter of minutes, not hours. And if it doesn't, well..." He sighed and looked down. "If it's actually that slow then it would become impossible to go back far enough. Too many variables, too many ponies she might have come across, so there's no point. So if we want to have a chance at solving this we have to assume whoever poisoned Princess Twilight did it here in Canterlot, after you two arrived. What that means is that we should go back through your path and look for clues there." He looked back up. "So?"
Rarity frowned in concentration for a moment. "You do have a point, darling. We can't afford to go back too much. Even if we just assume it was on the train ride, that's hundreds of ponies from all over Equestria. It would take days to check all of them, plenty of time for the culprit to hide. So we have to focus on Canterlot and the palace." She got up from her chair. "Let's do this, we've got no time to waste."
Smoke Screen nodded and got up as well.
Rarity walked up to Twilight. "Hang in there, darling," she said. She turned and walked out of the room, Smoke following behind her.