It’s easy to find mystery elements cross-pollinated to other genres, from sci-fi mystery to horror mystery and beyond; the same is true of romance. In part, this is because genre mash-up is fun! It’s also because mystery shares one thing in common with romance (equally pervasive in fiction) that neither shares with other genres: they’re more about structure than content. To be a mystery is to follow certain narrative conventions, involving certain character archetypes and hitting certain plot beats on the way to a certain kind of ending. Mystery provides a sturdy narrative skeleton and helpfully serves up tropes ready to be played with.
But there’s one combination, the sci-fi/fantasy mystery, that poses challenges other combinations don’t: How do you deviate from reality in enjoyable ways that don’t also break your mystery in half?
Without getting deeply technical, a mystery must be mysterious. On paper, this seems like a natural fit for speculative fiction—surely a genre that includes Jeff Noon (Vurt, The Body Library) and Yoon Ha Lee (Ninefox Gambit, Dragon Pearl) among its practitioners can manage “mysterious”? The trouble is that mystery requires something of a happy medium. Too out there, too far from something the reader can reasonably follow along with, and the twists and turns of the mystery can feel unfair. See: the contemporary reaction to Agatha Christie’s The Murder of Roger Ackroyd, whose big trick pales before the weirdness of, say, Noon’s Nymphomation.
How do you maintain narrative tension in the face of a character who can see through walls or control minds or, God help you, sort out truth from lies on a whim?Even if a writer manages to thread that particular needle, there’s the issue of the effect speculative elements can have on solving a mystery. In the same way horror suffers from a cell phone problem, speculative mysteries suffer from a scrying pool problem: the need to avoid instant win buttons that all-too-logically could exist. How do you maintain narrative tension in the face of a character who can see through walls or control minds or, God help you, sort out truth from lies on a whim?
And yet, in the realm of speculative fiction, none of those abilities are far-fetched, and questions about why such abilities don’t exist can ride on the coattails of seemingly unrelated world-building elements. If the spaceship is run by a sentient A.I., why doesn’t it know everything the detective needs to solve the problem? If magic exists, how has no-one come up with a spell to force people to tell the truth? Fortunately, the answers to this problem are as varied as the forms the problem can take.
You could build in the limitations for your speculative elements from the get-go, making the why of those limitations part of the story. If you have a magic system that logically could have a truth-telling spell in its repertoire, then maybe the spell was never created because the governing body that controls magical innovation isn’t willing to risk the political cost. Maybe the murderer was the victim of a criminal who escaped justice thanks to a lie, one which could have been caught by a truth-telling spell, now seeking vengeance on that governing body.
You could also impose limitations unique to the situation, beyond just extending the life of the mystery—in other words, rather than focusing on an extant why, you can introduce complications caused by the limitation being imposed. If the ship A.I. is shut down or corrupted, that can be used to ratchet up tension and create conflicts and obstacles beyond the mystery itself. Maybe your characters are so used to having the A.I. there to shore up their weak points they don’t know how to overcome fairly routine problems, or maybe there is now a ticking timer on the usable oxygen in the ship.
An answer that comes from the mystery genre itself is to use character arcs to short-circuit the instant-win buttons. In a modern mystery, the detective may have instant access to an expert or a witness via cell phone, but they could be lying about what they saw. Likewise, an all-seeing ship A.I. could be human enough to be convinced of the good that will come of the crime they’re covering for – or hey, what could a spaceship be blackmailed with? Or in the magical scenario, perhaps a charismatic culprit has convinced witnesses that some convenient lie is actually the truth, causing what they say to appear true even as it supports the fiction the antagonist has constructed.
There are more tricks available, but every solution boils down to three things: make sense, make it matter, and make it clear.
“Make sense” means that whatever you do needs to feel true. The disruption to the available speculative elements needs to be either baked into the world, or clearly explained, so that it doesn’t feel like the exception is just there to allow the story to be told (even though that’s totally why you did it).
“Make it matter” means the way you’ve molded the speculative elements to fit your story needs to have narrative resonance beyond allowing the story to happen, whether it’s a jumping-off point for political intrigue, married to a character arc, or whatever.
“Make it clear” means that the reader needs to be let in on the ways in which the speculative elements inform and affect the mystery. Show that character arc, explain that exception, build part of the world to be seen, and touched, and included; don’t try to make the mechanisms of your story mysterious, or it will be obvious that, yeah, this change was just made to let the story happen.
If you make sure everything flows logically, and that the reader is let in, a specific mystery can be incredibly liberating, allowing you to create unusual twists that a straight mystery simply cannot. It just requires a little extra work to block the reception on that scrying pool.