Dear Investigator (Casefic Exchange 2026)

[lostyesterday]

Hello, I’m lostyesterday on AO3. Thank you so much for writing for me! This letter includes my general likes and some specific ideas and prompts for each fandom I’ve requested. Feel free to use or not use the prompts in whatever way you want, including using elements of a prompt for a different character, relationship, or fandom than what I listed it for. Please also feel free to use whatever characters from canon or original characters you might need for your story in addition to the character(s) I’m requesting. And if you have a different idea unrelated to any of these prompts, please write it – I’m excited to read whatever you create!

General Likes

• Canon divergence AUs
• Worldbuilding (especially regarding fictional cultural practices, politics, etc.)
• Humor, hijinks, characters participating (willingly or unwillingly) in ridiculous shenanigans
• Unusual formats and styles (for example epistolary or anything nonlinear, first and second person POV are both great too)
• Hurt/comfort (physical or emotional)
• Time travel, time loops, temporal and spatial distortions – anything where time and space get weird
• Any type of stranded-in-an-enclosed/remote-place story (especially if it forces characters to confront aspects of themselves or their relationship with others)
• Dreams and nightmares, dreamscapes, ambiguity between dreams and reality
• Character studies, introspection, any in-depth look at the inner workings of a particular character
• Exploration of trauma, loneliness, self-hatred, and other painful emotions
• Feelings realization, getting together, established relationship – I enjoy all of these equally
• Friends to lovers, relationships where romantic partners are also best friends with each other
• Ambiguous relationships where characters aren’t sure how serious their relationship is/how long it will last/whether it’s romantic
• Characters trying to suppress or hide their attraction to other characters
• Messy relationships, arguments, fundamental differences in worldview
• Committed life-long platonic relationships/friendships
• Banter, jokes, witty exchanges
• Characters solving problems together and combining their skills in useful ways
• Characters having philosophical/moral discussions or arguments
• Characters having deep emotional connections with each other (healthy or codependent)
• Characters being understood in ways they never thought were possible

The Lord of the Rings

Merry & Pippin, Frodo & Merry & Sam & Pippin: 

• For the hobbits, I’d absolutely love any pre-canon low-stakes Shire mysteries! Maybe someone stole something from Bag End and now the hobbits are trying to figure out who it was and track the item down. Or maybe someone is trying to sabotage Sam’s garden (extremely high-stakes for Sam, of course).
• Post-canon Shire mysteries would be great as well. They could be similarly low-stakes (now with substantially more hardened hobbit investigators), or something higher-stakes involving the fallout from the scouring of the Shire. Maybe someone in the Shire is sabotaging their efforts to fix things after Saruman’s people were kicked out and they have to figure out who it is and how to stop them.
• There are other points in canon where it could be fun to set a casefic as well – either of the times the hobbits are in Rivendell, for example, or the time they spend in Minas Tirith near the end of the book with the rest of the remaining Fellowship.
• For all four hobbits investigating together, I’d love to see how each of their personalities interact in investigations. Who takes the lead? Who interviews witnesses and suspects? Who finds hidden clues? I’d love to see them debating and figuring things out through talking to each other about the case.
• For Merry and Pippin especially, I love when other characters underestimate them only for them to do something really clever, and I think that could be fun to play with in casefic too (as in, whoever they’re trying to catch thinks it will be easy to outwit them, but it isn’t so easy after all). I also love Merry and Pippin being both genuinely silly, but also using that silliness as a disguise to trick people into underestimating them.

Faramir & Gandalf: 

• I love the mentions in canon of their close friendship during the various times Gandalf came to Minas Tirith searching for information about the ring before the main plot starts. It would be fun to see the two of them work on some sort of scholarly investigation. Maybe they’re searching for an ancient text that was deliberately hidden, either in Minas Tirith or among old ruins. Or maybe they’re trying to decipher clues in an ancient text or map.
• Or maybe there’s a murder in Minas Tirith while Gandalf is there, and Faramir asks him to help investigate. I think it would be fun for Faramir to take the lead in this sort of investigation and Gandalf to take on a more advisory role.
• It could work well to have Denethor play a bit of an antagonistic role in any of these scenarios, hindering their investigation because he doesn’t like and is suspicious of Gandalf. I’d generally prefer if Denethor wasn’t depicted as evil or overly incompetent, but I absolutely love to see him being an asshole and irritating Gandalf.
• Involving Boromir in the story would be welcome too. Maybe Boromir goes missing and Gandalf and Faramir have to find him.

The Murderbot Diaries

Solo Murderbot:

• I would adore any mysteries or other investigations set in the Preservation Alliance! I loved Murderbot playing detective in Fugitive Telemetry, so anything spinning off of that would be great, especially since canon left the door open for plenty of other fun investigations to have happened between Fugitive Telemetry and Network Effect. Maybe Murderbot is called to help with another weird situation by station security – another murder or something different. Corporate kidnappings, elaborate assassination attempts – there are tons of potential situations where Murderbot’s investigative expertise might be useful.
• It would also be fun to see Murderbot have to deal with a low-stakes investigation that it doesn’t think matters at all but is for some reason compelled to help with. For example, maybe one of Mensah’s younger kids loses their favorite toy and Murderbot is tasked with tracking it down.
• For casefic set outside of Preservation, I love when Murderbot goes undercover as an augmented human on corporate controlled stations – to rescue a kidnapped person, find some vital piece of intel, or anything else.

Murderbot & Mensah, Murderbot & Ratthi:

• I love Murderbot’s friendships with Mensah and Ratthi, and I also think both pairs make great investigative teams. Anything I mentioned for Solo Murderbot could also work with Mensah or Ratthi helping Murderbot investigate.
• With Mensah, it would be fun to see her and Murderbot get involved with some sort of Preservation government related investigation. Maybe someone on the council is doing something very illegal and they have to figure out how to prove it. Investigations where the two of them are in active danger are great too – I love seeing these two desperately protect each other.
• With Ratthi, I think him and Murderbot as a crime-solving duo would be a lot of fun. I love the idea of him enthusiastically following Murderbot around to crime scenes like in Fugitive Telemetry. I also think it would be fun to see the two of them interview witnesses together – a mix of charm and intimidation.
• While I think the space between Fugitive Telemetry and Network Effect is a perfect place to set casefic, please feel free to set stories at other points in canon too! There are a lot of potential corporation-related cases these characters might find themselves wrapped up in at earlier or later points in canon.

Solo Mensah:

• I’d love to see casefic focused on Mensah during the span of time between All Systems Red and Exit Strategy where she investigates ways to deal with the corporates and sneaks around under their noses. I’m especially interested in what investigating under these circumstances might have been like for her while being under constant or near-constant corporate surveillance. Involving any of the other Preservation characters in the investigation would be great too.
• During the same span of time, I’d also love a canon divergence story where Mensah actively tries to find Murderbot, either because she believes it’s in danger or for some other reason. I’d love to see her follow its trail and try to piece together clues of where it’s been and what it’s been doing, maybe gathering information from interviewing the various people Murderbot meets in Artificial Condition and Rogue Protocol.
• Mensah-centric investigations set in Preservation either pre-canon or around the time of Fugitive Telemetry would be great too! I think there are a lot of potential cases she might have gotten wrapped up in through her governmental position.

Solo Three, Ratthi & Three: 

• Three is such a fun character to put in situations, and I’d love to see it solve a case, either by itself or with Ratthi. I love seeing Three figure out how to make its own choices now that it’s free, and casefic where its friendship with Ratthi develops alongside and through the investigation would be extremely welcome.
• I love stories about Three going to Preservation, so any investigations on Preservation with Three being called in as an expert the way Murderbot was would be great. It would also be fun to see it making friends with the Preservation bots through its investigation.
• It would also be interesting to see Three go undercover as an augmented human, either accompanied by Ratthi or not. Maybe it needs to infiltrate a corporate station to gather an important piece of intel or find a kidnapped person.

Murderbot & Three:

• A lot of the prompts above for these characters separately could work with the two of them together as well. Overall, I’d be really interested to see how their different ways of interacting with the world mix in an investigative context. What sorts of things does each of them see that the other misses? Seeing their relationship develop through working together on an investigation would be great too.
• Any cases where one of them is in trouble (kidnapped or something else) and the other has to find/rescue them would be super great too.

Star Trek: Deep Space Nine

Solo Jake:

• I love Jake a lot, and I think his curiosity and interest in journalism make him a really fun character to focus on for casefic. Maybe Jake decides to write a piece about a new trade route that’s being established through DS9, only to discover it’s a cover for some kind of illicit activity. Or maybe he accidentally discovers a criminal secret Quark is keeping and has to figure out what to do about it.
• I love when Jake’s enthusiasm and curiosity cause him to get into situations way over his head, so any story where his investigation turns up something much bigger than expected would be fun. I also love the episodes focused on him that are filled with humor and hijinks, so very low-stakes and silly investigations would be great too.

Jake & Nog:

• The powerful friendship between these two is so special to me. I love how silly they are sometimes. I love to see them argue and have different perspectives but at the end of the day always remain the closest of friends. In an investigative context, I think they have a fun back and forth as they figure things out and try (and usually fail) to minimize the chaos.
• It’s always fun to see these two get involved in ridiculous situations that spiral further and further from what they originally intended (like the episode “In the Cards”, for example). Maybe Nog reluctantly agrees to help Jake investigate something for a journalism piece he’s trying to write and they stumble into a larger mystery. Maybe an item Nog wasn’t supposed to be borrowing in the first place gets stolen and he and Jake have to track it down and get it back before anyone notices.

Jake/Ziyal, Jake & Ziyal:

• Canon never letting these two interact was such a missed opportunity. They have a lot in common (artistic passions, a mother who died when they were young) while also having super different life experiences in other ways and opposite kinds of relationships with their fathers.
• I equally love this relationship as platonic or romantic, and if you do write their relationship as romantic, please don’t feel it’s necessary to make it super shippy. This is a casefic exchange, so whatever romance there is can be totally secondary to the main plot. That said, I love seeing the two of them gradually develop feelings/get together, and I love scenarios where they have a long-term secret relationship, so feel free to include any of that if you want!
• One of my biggest casefic desires for these two is to see them work together during the Dominion occupation of DS9 in season 6 to secretly resist the Dominion and fight back. I’d love to see Jake and Ziyal investigate something the Dominion is planning and figure out how to stop it, maybe with Ziyal pretending to be fully on board with the Dominion to gather information and then meeting with Jake in secret. Or maybe they’re on a mission to figure out how to sabotage something of the Dominion’s without being caught. Any involvement of the other main resistance characters on the station at this point in the story like Kira and Quark would be great too, as would involving Weyoun, Damar, or Dukat as major antagonists.

Jake & Nog & Ziyal:

• I think these three would be such a fun and chaotic trio. I’d love to see them work together to solve a case by coming up with increasingly wild theories and plans of action that somehow end up all working out in the end. A lot of my prompts for the individual relationships above would work here too, like Jake roping the others into helping him investigate something for a journalism piece he’s working on or the three of them trying to find some sort of missing item along the lines of “In the Cards”.

Jadzia/Kira, Jadzia & Kira:

• I love these two whether their relationship is romantic or platonic. I love how close their friendship is despite their very different histories and backgrounds. I’d love to see them work together on an investigation, and how their different approaches to the world might inform how that investigation unfolds.
• If you do write their relationship as romantic, don’t feel pressured to make the story super shippy. Them being in an established relationship as a background thing would be great. Stories where they admit their feelings and get together while working on a case would be super welcome too.
• I love to see these two deal with weird sci-fi investigations. Maybe they’re stranded on an alien planet where some mysterious entity is threatening them, and they have to work together to figure out what it is and how to stop it. Any sci-fi situations connected in some way to the Prophets would be interesting too. I’d love to see how Kira with her religious perspective and Jadzia with her non-religious scientific perspective work together to solve a case that relates to Kira’s religion.
• I’d also love to see these two in more actiony cases where they have to team up and use their combat skills. Maybe someone’s been kidnapped and they have to locate and retrieve them.

Jadzia & Kira & Sisko, Jadzia & Sisko, Kira & Sisko:

• I love these three and I love each of their dynamics with each other. I always wished the show had them interacting more as a trio – sort of like the command trios in other Star Trek shows. I’d love to see how they work together and solve problems together with their very different perspectives. I love Sisko’s individual friendships with Kira and Jadzia too.
• Dax and Sisko’s friendship that lasts across lifetimes is wonderful, and I love scenes where they debate problems together. In an investigative context, I think they’d spend a long time passing theories back and forth and challenging each other to push to the end and solve the case.
• I love the progression of Sisko and Kira’s relationship from antagonistic to awkward to close friendship over the seasons. Having them work together to solve a case early on when they still don’t feel comfortable with each other would be fun, as would a story set later when they’ve become good friends and work together really smoothly.
• For any of these combinations of characters, Defiant missions are always fun. Maybe they’re in the Gamma Quadrant and they have to find a saboteur aboard the ship (changelings impersonating various characters are welcome). Maybe they have to go down to an alien planet to find and rescue a missing crewmember. 
• With Jadzia and Sisko, it would be interesting to see them work on a case related to one of Dax’s past hosts. Maybe someone is murdering all of Curzon’s friends from a certain time period, and they have to figure out who it is before they come for Jadzia. 
• With Sisko and Kira, it might be interesting to see them work on a Bajor related case. DS9 mostly abandoned the search for the Orbs of the Prophets as a main plotline, so it would be cool to explore that. Maybe Sisko and Kira have to piece together clues to find one of the lost Orbs.

Star Trek: Enterprise

Solo Hoshi: 

• Hoshi didn’t get many chances in canon for her investigative skills to take center stage, which I think is a shame. Translation is a form of investigation – piecing together clues and context to come to as best an understanding as possible of what another person is trying to communicate.
• Any investigative stories starring Hoshi working on translations of some kind would be great – deciphering alien texts to try to find a way out of a trap Enterprise has gotten into or trying to figure out how to communicate with an incredibly alien species when the universal translator doesn’t help.
• It would also be interesting to see Hoshi investigate something outside of her typical area of expertise, like a murder mystery. I’d love to see Hoshi lack confidence in her ability to figure things out in the beginning, only to surprise herself by doing a great job investigating.

Hoshi/T’Pol, Hoshi & T’Pol:

• With Hoshi and T’Pol, I’m happy for their relationship to be romantic or entirely platonic. If you do write Hoshi/T’Pol, anything from secret unspoken attraction to established relationship would be very welcome. I love stories where they have a weird/messy relationship – for example, they’re sleeping together but won’t admit they actually have feelings for each other or believe their feelings are unrequited. A sweet and happy relationship between them is very welcome too, though.
• T’Pol being involved in any type of translation-related case would be fun, especially since she often works with Hoshi on decryption and other similar tasks in the show. I’d love to see the two of them working together to solve puzzles and piece together clues. I love seeing them both being competent and valuing each other’s skills.
• Away mission stories where the two of them have to investigate something on an alien planet would also be great. It would be fun to see them go undercover and pretend to be from that planet in order to search for a missing crewmember or something similar. If you want to write something shippy, then maybe circumstances force them to go undercover as a couple and they’re both uncomfortable about it.

Star Trek: The Next Generation

Solo Guinan: 

• I love Guinan, and I think her position as bartender and “listener” would make her an interesting investigator since she obviously knows a lot about everyone else’s business. I love how, in conversations with other characters, she often sort of manipulates them into seeing things differently or admitting things they weren’t planning to, which could be very fun in an investigative context.
• It would be fun to see her solve a mystery without ever actively deciding to investigate – people just keep coming into Ten Forward and telling her things about whatever the mystery is, and she puts together the pieces from there.
• I’d also love to see her take a more active role in investigating. Maybe a crew member is suspected of having committed a crime, and Guinan believes they’re innocent, so she sets out to prove their innocence (I’m thinking something along the lines of the episode Ensign Ro but with a more actively investigative vibe).
• If you have ideas for it, I’d absolutely be open to a story set pre-canon during any point in Guinan’s very long life, either something historical set on Earth or somewhere else entirely. I’m open to involving elements or characters from TOS or Enterprise for casefic set pre-TNG if you’d like.

Data & Guinan: 

• I think these two have a fun dynamic, and it would be great to see how they work together in an investigative context. They have super different perspectives on and approaches to life, but both are very good at figuring things out. I’d love to see detailed discussions about the facts of a case between these two, analyzing various theories and considering things from all angles.
• A lot of the ideas I mentioned above for solo Guinan could work with the two of them. I love the idea of them each separately interviewing witnesses/suspects and then coming back together to compare their findings.
• I always enjoy TNG episodes where some weird alien thing affects the ship and everyone is incapacitated except Data who has to save the ship, but I think it would also be super fun if Guinan wasn’t affected either and the two of them had to work together to figure out what was wrong and how to stop it.

Star Trek: Voyager

Solo Tuvok:

• I love when Voyager gives Tuvok a mystery to solve! He’s such a fun detective, and I love his methodical and rational approach to solving cases. Any canon-typical mystery or other type of case set at any point in the series would be great. If you have ideas for pre- or post-canon stories I’m very open to that too, but all my prompts and ideas will be for stories set during Voyager.
• Classic murder mysteries are always great. Maybe yet another Voyager crew member has been mysteriously murdered and Tuvok needs to find out who on the crew did it. Maybe an alien ambassador came aboard to negotiate with Voyager for supplies before being murdered, and Tuvok has to prove no one on the crew did it.
• I also think any type of locked room mystery/impossible-seeming crime would be really fun with Tuvok. He needs to believe in a logical explanation for everything, so how does he deal with “impossible” situations?
• Investigations that involve the more actiony elements of Tuvok’s job as Chief of Security would be fun too, like finding and rescuing a kidnapped crew member or trying to stop a mysterious alien force from killing someone onboard the ship by investigating and identifying it.

Seven & Tuvok, Kes & Tuvok:

• Seven and Kes are both characters I think it would be super fun to see team up with Tuvok to solve a case (including any of the above prompts I listed for solo Tuvok). I love each of their dynamics with Tuvok, and I think they’d play off of him in different interesting ways in an investigative context.
• Seven might take a similar approach to Tuvok in a lot of ways, trying to come up with precise rational explanations for things and account for all the potential variables. I especially think it would be fun to see the two of them tackle a mystery that seems at first to be completely impossible or nonsensical. I’d love to see their careful process of working rationally toward the solution.
• Kes on the other hand tends to take a different approach to Tuvok – a more intuitive and open-minded approach. Kes would be open to all sorts of wild possibilities, no matter how unlikely. I love how much respect Tuvok and Kes have for each other despite how different they are, and I’d love to see them have detailed discussions about the case as they’re solving it, or interviewing witnesses/suspects together. Any involvement of their telepathic abilities would be great too.

Chakotay & Janeway & Tuvok:

• I love to see these three working together as a command trio debating issues and figuring things out. I love when they disagree and see things from different perspectives. I love when Janeway acts as a balancing force between Chakotay and Tuvok when there’s tension between them, but I also love when Chakotay and Tuvok unite to stop Janeway from doing something they both agree is a bad idea.
• Typical monster of the week plots or any other canon-typical investigation would be great here. Maybe something weird is attacking Voyager and they have to figure out what it is and how to stop it. Maybe a crewmember has been kidnapped and they have to figure out where they are and how to get them back. Maybe a trader they’re dealing with is behaving suspiciously and they have to figure out how they’re being tricked. Maybe someone on the crew is an imposter and they have to identify them.
• I also love more humorous and light-hearted investigations for them. It’s always fun to see characters used to dealing with life-or-death situations investigate a relatively minor problem. Maybe someone is rigging Voyager’s holodeck Velocity tournament to make certain people lose and they have to figure out who. Maybe someone is stealing from Neelix’s store of seasonings.

Seven/B’Elanna: 

• I love these two so much and I love seeing them work together! Please don’t worry about having to write something super shippy unless you want to – this is a casefic exchange and the case is obviously the primary focus. I’d love a story where they’re in an established relationship while solving a case, or a story where one or both of them has feelings for the other that aren’t directly related to the plot. But if you do want to write a “slowly realizing mutual feelings and getting together while working on a case” story I’d absolutely love that too!
• I enjoy these two being antagonistic and having difficulty working together, but I also love seeing them finally get past their differences and make a formidable team. In investigative contexts, the way they push back against each other could be both a hindrance and a benefit in solving the case.
• Given each of their jobs, engineering or science related investigations are the most obvious type of plot for them to play the main role in. Maybe something or someone is sabotaging Voyager and they have to figure out what’s happening and how to stop it. Maybe the case involves a malfunctioning holodeck that the two of them are called to fix.
• I also love seeing these two on away missions together. Maybe they’re on a weird alien planet trying to investigate and identify the bizarre thing that’s trying to kill them before it’s too late. Maybe they’re searching a creepy abandoned space station for something they need.

Seven & Kes:

• I love AUs where Kes stayed on Voyager after Seven came aboard, and I adore the concept of them becoming friends. They’re both so weird in completely different directions, and I think they would be drawn to and encourage each other’s weirdness. How would they work together in an investigative context?
• I think it would be fun to see these two investigate strange and bizarre phenomena. Maybe something is slowly chewing through the ship and they have to figure out what it is and how to stop it. Or maybe they go on an away mission together and end up stranded on one of those weird alien planets where nothing makes sense and they have to solve the riddle of what’s happening in order to escape.
• Low-stakes mysteries with these two would also be great. Maybe someone keeps taking Seven’s favorite phase compensator and Kes agrees to help her figure out who.