Written for DesertVixen on AO3 as part of Space Swap 2021.

"Oldemar III," said Captain Pike, taking in the snowy and mountainous planet on the viewscreen. "One of my professors at the Academy was on board the Archius as a young man when it visited eighty years ago. He used to talk about it in lectures as an example of cultural contamination – I'll be interested to see how the planet has changed."

Number One shook her head. "The report that survey ship sent back wasn't very hopeful, presuming their observations from orbit are accurate. I can't imagine, though, why the Oldemarians would abandon their attempts at flight, however primitive, because they encountered a starship. One would think it would only increase their interest."

Uhura looked up from her console. "Unfortunately, past examples of contamination haven't been that simple. I've been helping Historian McIntyre with some research. There's not much that's been studied – it's a good thing we're here – but Saqa IV devoted its workforce to violin concertos after a Starfleet physician told one resident they were 'fit as a fiddle,' and Ochesca II was utterly ruined because of a single forgotten phaser."

"In other words, then," said Number One, "we have no idea how the planet has been affected."

Uhura nodded. "That's correct. We only know a few details about the Oldemarians. They were reported to have an extremely rigid sense of right and wrong. Also, given the inhospitable nature of their planet, their evolution so far has been a bit unusual – as of when the Archius visited, their population consists of only a few individuals with extremely low reproductive rates. Instead, individual generations are long-lived and extremely adaptable."

"That is consistent with my scans," noted Spock. "There are only eleven life signs present."

Pike stood up and checked his communicator and phaser. "They shouldn't have developed into too much of a threat, then, and we should begin. I realize Oldemar III isn't a very comfortable place, but it's at least a change of scenery and no one has been off the ship in too long – I'll bring a fairly large away team. Number One, Spock, Tyler – come with me. You'll need cold-weather gear –" He glanced at the viewscreen again. "– but I'm sure you are well aware of that already. Uhura, summon Villarreal, Ruiz, and Sridhar from Security and Yeoman Colt. I suppose we'll also want McIntyre, Wagner, and Abebe for their expertise."

"Right away, sir."

"One moment –" Number One broke in. "Take Kent as well. I realize this is hardly her usual field, but we were talking in the mess the other day and had quite a fascinating conversation about old Earth media and cultural practices. It's a hobby of hers. She might be useful and has been having to practically live in Engineering lately."

"Good," said Pike with a nod. "Uhura, you have the Conn. Direct everyone to the transporter room as soon as possible." By this point he had already almost left the bridge.

"I'd say someone is eager to go." Number One chuckled. "I had better catch up."

Twelve Starfleet crewmembers materialized in a cloud of howling wind and blowing snow. What light there was was weak and dispersed. Everyone shivered and retreated into their hoods.

"Captain," said Spock, having to shout to be heard over the wind, "this location should be near their cluster of dwellings. They appear to be buried or gone entirely." He pulled out a tricorder and took a step forward, only to suddenly disappear below the surface of the snow.

The rest of the away team rushed over. "Mr. Spock!" cried Tyler. "Are you all right? What happened?"

Spock gingerly stood up, his head still several feet below the others. Bare rock was visible underneath the scattered snow by his feet. "I appear to have fallen into a tunnel of some sort dug into the snow. My weight was too much for the icy crust on top to bear and so this section collapsed. But yes, I am 'all right.'"

"Can you see where the tunnel leads?" asked Pike.

"I believe we have found the residences of the Oldemarians. What is left of this tunnel seems to connect two doors."

"That's a start at least," said Number One.

"If you don't mind if I interrupt – can you tell anything about the materials used to construct these doors?" asked Wagner, the ship's archaeology and anthropology officer. "That might give us an idea of how advanced these people are."

Even Spock startled slightly as a sudden voice with a pronounced French accent echoed down the passageway. "That will not necessary – Monsieur Spock, correct?"

"Yes," managed Spock.

"Parfait. I can introduce you to our little train myself. I am Monsieur Hercule Poirot." By now he was standing in the collapsed tunnel section next to Spock, clearly analyzing the group above him who in turn were doing much the same to him. Finding an appropriately descriptive adjective for this M. Poirot was difficult to say the least – perhaps fastidious, or dandified. He was wearing a gray three-piece suit and matching bowler, a bowtie, and the most exquisitely trimmed and curled mustache.

"Excuse me," asked Kent, Chief Engineer and historical Earth aficionado, "you said your name is Monsieur Poirot?"

"Oui, Madame! Hercule Poirot at your service."

"It is a pleasure to make your acquaintance, Monsieur." She turned with eyebrows raised to Wagner and McIntyre, the ship's historian. "Well, I believe we've found the source of the contamination," she murmured.

Further talk would have to wait, though, as Poirot invited them to jump down through the collapsed tunnel roof and come inside to warm up and get acquainted. One by one everyone landed with varying degrees of dignity and the group was conducted through one of the doors and into a small room set up like a dining car in a 1930s train. Tables covered with fine white tablecloths were bracketed by solid armchairs, while the wood paneling on the walls was polished to perfection. Large windows provided majestic views of the inner workings of snowdrifts.

On the way in Kent quickly whispered her suspicions to Pike. "The contamination was caused by a book, sir – a mystery novel from the 20th century featuring a detective named Poirot."

He nodded quickly and passed this on to Number One.

Once everyone had filed inside the "railcar" Poirot shook hands and greeted each individual and then called and introduced the other Oldemarians. These other ten Oldemarians all had one of two names – Bouc or Constantine, and were numbered Bouc I through V and Constantine I through V to distinguish them.

"Welcome to Oldemar!" Poirot was positively beaming. "We haven't had any visitors in so long. We all mere children for the visit of the Archius, which did so much for our petit society." He picked up a book from a nearby table. "Our guiding text in this world, the Murder on the Orient Express. It has given us an enlightened way of life and knowledge of our journey towards our goal."

"Please, continue," said Kent.

"Of course. There was a murder of a man here on Oldemar, you see. It was long ago but we mourn him still." He dabbed his eyes with a handkerchief. "According to the book, the suspects will be found – that is my duty, in fact. But we are eleven, while in the book there are twelve, and so we have made no progress –" He halted, suddenly, inspecting the away team again. His joviality faded, replaced by apprehensive wonder.

Kent stiffened, realizing what was coming.

"Twelve. Twelve murders, five women and seven men – you are twelve, five women and seven men." He thew up his hands in perverse delight. "We have done it! We have found them, mon Dieu! Seize them and lock them in the next car, les diables!"

The entire away team was quickly forced by a cluster of Boucs and Constantines equipped with knobbed walking sticks and knives back through the collapsed tunnel and into the next building, this one outfitted with a long corridor and passenger compartments complete with beds and luggage. One of the Boucs seized the closest officer, an exobiologist named Abebe, and pressed the tip of the knife against his chest. "You will surrender your weapons and communicators, or he will be stabbed twelve times!"

The team reluctantly complied.

"Good! You will stay here to await your judgment." The door slammed shut.

The only sound for the next few moments was the howling of the wind, still faintly audible through the packed snow.

"It appears we can conclude that contamination has been quite extensive," said Spock, quite unruffled.

"Yes indeed," said Pike. He rattled the door, tried to force it, and hollered at the Oldemarians. Recognizing that these attempts were as futile as they had been on Talos IV, he relented. "Kent – you said this is all the result of some misplaced novel?"

Kent nodded ruefully. "That seems to be the case, unfortunately. The book in question is Murder on the Orient Express, perhaps the most popular of a 20th-century detective series featuring a Hercule Poirot."

"I think I remember that book," said McIntyre. "Christie or something like that, right?"

"Correct," said Kent. "In any case, the story takes place in a snowed-in train. I'm guessing the arrangement and furnishings of this settlement are intended to mimic that."

"That may also be why they seem perfectly comfortable staying trapped under so many feet of snow," suggested Number One.

"That makes sense," said McIntyre. "And if I'm remembering the book correctly the Oldemarians are also all named after the characters that aren't involved in the murder."

Kent nodded, and then sighed. "As for the reason we're all under lock and key right now – the murder in the book itself was revenge for a previous kidnapping and murder of a young girl. Twelve people with various connections to the original victim found and killed her murderer. Unfortunately, by sheer bad luck, we're also a party of twelve, and by even worse coincidence the proportion of women to men is also identical."

"Impressive," said Number One dryly.

Kent snorted. "Yes. From what this 'Poirot' was telling us, it sounds like there was a similar murder committed here, and so when the book was left behind it was a perfect match and they considered it a prophecy, so to speak, of what was to come. Our arrival fulfilled that and now they think their case is finally resolved."

"How did this book end?" asked Pike.

"Given the crimes of the victim, Bouc, Constantine, and Poirot agreed not to report what had truly taken place to the police, who would instead be told that a stranger had boarded the train, committed the murder, and then disappeared into the snow."

Yeoman Colt spoke up. "I don't understand – in the book, the twelve were released? Why are we being held?"

"Uhura was completely correct when she mentioned their strict moral tendencies," said Wagner. "They've evolved in an inhospitable and dangerous climate, where things tend to be quite binary – warm or frigid, sheltered or exposed, and so on. There's a very fine line here between safety and freezing to death. For some reason in this case that black-and-white sort of existence seems to be also evident in their moral code. There's just not space for gray areas like there were in the book, and they seem to consider murderers to all be alike regardless of motivation. It's quite fascinating, really!"

"Quite," said Pike, clearly not completely in agreement. "In short, they seem to be changing the ending."

"They are changing the ending," Kent confirmed.

"But what are we going to do about it?" Ruiz from security was the least seasoned person present, which was quite evident in his tone. He pushed against the door that had closed behind them. "We're locked in with no phasers or communicators!"

"We're temporarily being left alone and have time to plan. I wouldn't get too concerned." Chief of security Villarreal was accustomed to handling jumpy newcomers.

"Yes, ma'am."

"The kid's not wrong, though, if I may so," said Sridhar, also of security. "Discussing ancient history is all well and good but soon-to-be history won't be too pleasant if we don't figure out how to get the hell out of here."

"That's also true," said Pike. "I must confess that I'm not especially familiar with xenoanthropology and three-hundred-year-old fiction. Kent, Wagner, McIntyre – what would you suggest?"

"We need to win them over somehow – establish that we're the good guys here," said Wagner.

McIntyre grimaced. "That's going to be difficult to say the least, since they're so thoroughly convinced that we killed one of their own."

After a long pause Kent spoke. "Suppose – suppose we try to help them solve their case. I realize it's probably decades old at least, but the attempt might make them slightly more inclined to look on us favorably and in the small chance we do come up with something we'll have some solid evidence to prove we're not who they think we are."

"That's an excellent idea," said Number One. "The only issue is that no one is around to interview."

Pike considered this. "I'm sure we can make some noise and they'll turn up. Let's give it a try." He walked back to the door they had entered through and started pounding on it again. "Hey! Anyone? We would like to help you here."

This attempt was more productive. Some grumbling filtered through the door before the voice of the Bouc who had threatened Abebe spoke up. "What do you want? We're not interested in your help. You're murderers."

Pike attempted a conciliatory tone. "We're not, M. Bouc, but there's no purpose in arguing about that right now. What we'd like to do is just ask some questions about the murder, to –" He glanced at Number One, who quickly mouthed something. "To investigate your claims."

"What's that supposed to mean?"

"That's an offer of help."

"Let me ask M. Poirot." The voice stomped off, but returned sounding somewhat more amenable. "Fine. What would you like to know?"

"What do you know about the victim and his death?"

"He was named Cassetti. He made us strong and tough enough to survive. He was stabbed twelve times. But you already know that, of course."

Pike decided to ignore that jab. "I see – those are indeed the facts. But did you know him personally? What was he like, and how long ago was this?"

"He was –" the voice stumbled. "I don't know, really. I think he was before my time. I've heard all about him from the others."

"And what do they say about him?"

"They say he was a leader – I'm not sure. Why don't you ask them yourselves?"

"That would be very helpful, Bouc."

The subsequent interviews were no more illuminating, however. "I suppose this is what we get for trying to solve a case that is who-knows-how-old," said Number One.

"At least these beds are really comfortable," piped up Tyler from one of the passenger compartments. "There are worse places to be stuck."

"They've got to be getting worried by now up on the Enterprise, since we haven't made contact," said Pike, pacing up and down the corridor and attempting yet again to try forcing the door with no success.

"What's the worst they could do to us?" asked Colt.

"Given the climate of this planet," observed Spock, "they would simply need to leave us outside without cold-weather gear or communicators. We would likely experience death by hypothermia before the Enterprise found us."

"Great," said Ruiz. "Death. Nothing to worry about."

"That's enough," said Villarreal.

Throughout all this Kent had been slumped against a wall, eyes not quite focused and mind somewhere else. Suddenly she straightened. "What if we're heading off on what they call a wild goose chase?"

"Explain," urged Pike.

"What if there never was a murder here on Oldemar? Everything else about the case they believe to be factual is fabricated, so why not this as well? Perhaps instead of the book fitting in with existing events they were simply vulnerable enough to contamination to have invented all of it? By now it's been long enough that they couldn't be blamed for not knowing the difference."

Number One considered this. "You know, I'll bet you're correct. It would explain why they all seem so unsure of the details of the man. In fact, I can't believe we didn't think of this earlier!"

Pike grimaced. "Well, the absurd circumstances we've found ourselves in certainly wouldn't aid rational thought. But I do think you're probably correct. I'm not sure I see another explanation."

Wagner nodded. "I'd have to agree. Cultures usually pass down more specific, personal details about events that have this level of impact on collective memory, even if they've warped or been invented altogether over time."

"Again," interjected Villarreal, "the question is what to do with this information."

"I see three options," said Pike. "To devise an escape plan ourselves and hope that it works and the Enterprise finds us before it's too late, wait for rescue and hope the Oldemarians continue to leave us unharmed, or reveal the truth and hope they can handle the fact that their entire civilization as it stands is based on fiction."

"The first two options are of course very risky, but the last would just cause even greater contamination," said Wagner.

"Would it, though?" asked Number One. "If we reintroduced them to what we know about their culture before the Archius – maybe gave them all the files and records we have – perhaps they would adapt to that as readily as they have to Murder on the Orient Express. They might actually resume their natural evolution."

"That's possible," allowed Wagner, "but remember that contamination and contact function in unusual and unpredictable ways."

"We also have to take into account the possible dangers of leaving the Oldemarians as they are," said Villarreal. "I'd be worried that some other group of travelers could stumble into the same situation we have and not have a starship to back them up."

"I am aware that Starfleet does not yet have regulations on the subject, merely recommendations, but the Vulcans have long made a practice of avoiding cultural contamination at all costs," Spock stated.

Pike almost renewed his pacing but stopped as Number One put a hand on his arm. "Can 'at all costs' include sacrificing eleven of my crew and myself?"

"Yes, Captain."

Pike squared his shoulders. "My apologies to the Vulcans, then, but I won't have the loss of so many good people on my hands. We will tell them about the book, and give them the files from the Archius as Number One suggested. I don't like it, but I have to put the safety of my crew first."

Wagner looked away, but nodded reluctantly.

After careful planning and some rehearsing Pike had requested a meeting with Poirot and the rest of the Oldemarians. This request was reluctantly granted and the away team conducted back to the dining car.

Poirot glanced up from a tattered morning paper. "What do you have to say for yourselves? The little gray cells shall make themselves… temporarily available."

"Thank you," said Pike stiffly, and Number One gave him a little nod of encouragement. "We have been greatly impressed by your resilience in your search for truth. We would like to make sure you are fully aware of the facts of the matter, as I'm sure any detective would want to be."

Poirot gave a curt nod.

"I thought so. You see, in the Federation we sometimes write books that are called fiction – stories from our minds, rather than stories from reality."

Poirot began to grow red at a frankly astonishing pace. "Do you dare suggest le bon livre is an invention?"

Pike moved to reassure him. "I mean no such disrespect. Your book was written by one of the most well-known writers of old Earth. She was renowned for her ability to write works with impressive twists and turns. Have you never amused each other with tales you've created about the unknown and the mysterious?"

Poirot did his best to look disdainful, but he couldn't avoid the nods and mutters of assent from the Boucs and Constantines.

"You are correct in judging this book to be a masterpiece and an inspiration, and the fact that it is a work of fiction does nothing to diminish that. But you've carried its burdens with you, too – the idea that one of your people was killed. That is part of the book, not reality, and thank goodness for that."

"These are just the words of a desperate man trying to escape what he deserves," Poirot snapped.

Pike opened his mouth, closed it, and looked to Number One for help. She stepped in. "Perhaps, but you can't deny the facts. None of you knew him personally, and none of you have any solid idea of who he was. His character in the book was a gangster, so of course you can say he was tough. But none of you truly know the man himself, because he never existed."

Now it was Poirot who was at a loss for words. One of the Constantines stepped out of the shadows. "If all this is true, what are we to do with our lives from here?"

"Ah," said Number One. "You can do so much. Before the Archius visited you were looking to the stars, not burying yourselves under the snow. You had begun to build flying machines, and the bravest took short flights through the sky. You could continue – improve your engineering until you could fly among the stars as you once wanted to. We can give you copies of the data the Archius took, which have more details. You could begin again."

Even Poirot was beginning to look entranced, but still seemed determined to be resistant. The Constantine hesitated, and then spoke again. "All right. We'll take you at your word. We've spent too long ignoring the facts of our past. Send us those records, and we'll attempt what you described."

Poirot sputtered at his sudden loss of authority. "Who are you to –"

"Who are you, I might ask instead, to continue to keep us down here?" She walked to a pile of phasers and communicators on a table in the far corner, picked them up, and began to return them. "Return to your ship, send us your files, and depart in peace. I'm sure we're all very sorry for the confusion." She shot a glare at Poirot, who at least attempted to look contrite. "When we're ready we'll contact the Federation. I hope that will be soon."

Pike shook her hand. "I hope so as well. Thank you." He flipped open his communicator. "Pike to Enterprise –" He got no farther.

"Captain!" exclaimed the voice of Doctor Boyce. "We were getting worried up here that you'd run off to play in the snow or something."

"What Doctor Boyce means to say," Uhura smoothly interrupted, "is that we're all very glad you are safe, sir."

"Thank you both very much. Twelve to beam up."

"Yes, sir."

Pike stepped back onto the bridge of the Enterprise and settled back into his seat with a contented sigh. "It's good to be back. Uhura, have you transported those files down to the planet?"

"I have, sir."

"Excellent. Helm, lay in a course for the nearest starbase. We could all use some time off the ship – somewhere where we're not being accused of murder, that is. Maximum warp."

"Course laid in, sir."