I guess the first question is really this: What is the Flux Capacitor?
Easy:
…it’s what makes time travel possible.
And that’s all you need to know.
What a great bit of storytelling! The entire Back to the Future franchise rests on the ability of Marty McFly and Doc Brown to travel through time in their suped-up DeLorean. But do we really need to know how time travel works? Nope. We just need to know that it does.
Therefore the Flux Capacitor makes time travel possible and it also makes the story possible. All without being explained in the slightest.
So the real question of this post is: What makes a story possible? What is it that a plot relies on to make all the action which follows it make sense? If you are writing a story, do you know what is special about your story which allows it to happen?

A flux capacitor is more that just a plot device. All plots use devices of one kind or another to drive the story forward, whether it be a character introduced at exactly the right moment, or an object which all of the characters suddenly must possess. But, especially in speculative fiction, the flux capacitor is an element of plot which makes the story not only possible, but plausible. It sets the rules for the story-world (even if it does not necessarily explain them), and allows readers to willingly suspend their disbelief and move through that world. Even if the story’s flux capacitor does not operate by the rules of the universe as we know them, it must operate according to the rules of that particular universe. Otherwise the reader throws the book across the room in disgust (or deletes the ebook from their Kindle).
Some other examples of flux capacitors:
- The ability of Dr. Frankenstein to create the monster. Going back to one of the great novels of speculative fiction, Frankenstein, the ‘process’ by which Victor Frankenstein creates his new-man is never fully explained (for obvious reasons). But there is no story without it. Again, it is a flux capacitor because it doesn’t just drive the plot forward, it creates the plot.
- The ‘box’ in Under the Dome. The technology behind the box is never fully explained, nor how it came to the town of Chester’s Mill. And nothing in the story would have happened without the interference of the dome that the box generates. The dome going up is the plot’s inciting incident, but the box itself is what makes the story possible and gives the rules which the world of ‘the dome’ operates under.
- The drink ‘True Blood’ from the TV series or Sookie Stackhouse novels. Again, the technology is sketchy at best, but the real reason it qualifies as a flux capacitor is because it is the hinge which opens the door between the human world and the supernatural world. The events of the story wouldn’t unravel the way they did (therefore there would be no story) if the world of Bon Temps hadn’t been changed by humans now knowing of the existence of vampires, etc.
In fact, the ‘rules’ for any supernatural / alter-natural creature, from vampires to zombies to aliens might qualify as a flux capacitor if those rules are the fulcrum for making the story possible. The characteristics of these species or monsters change from world to world as each author imagines them anew (just compare the vampires of Twilight to those of Dracula). But each must be consistent within their own world or face serious criticism from readers (and outright rage from the anti-fans of the story).
Technology, also, such as the TARDIS from Doctor Who or the ‘timer’ from Sliders (jeez, I’m old!) is also often a flux capacitor due to the fact that the story would not take place without it and its mere presence ‘explains’ how the story happens.
Note that an item being powerful, such as the Ark of the Covenant in Indiana Jones, does not necessarily make it a flux capacitor. You could substitute any awesome item for the Ark and Indiana Jones would still go off to save it (see Holy Grail and Sankara Stones and Crystal Skull!). These things are your run-of-the-mill plot device.
What do you think? Do you see the flux capacitor as a specific type of plot device? Which other ones are great examples of devices which makes a story not only possible, but plausible?