First, go and watch The Force Awakens and The Last Jedi.

J. J. Abrams has this storytelling device which he uses, which he calls a "mystery box". Me just telling you those two words, and then pausing for a little while as you think about all of the works of J. J. Abrams you've ever seen, might be enough for you to work out what a "mystery box" is all by yourself.

The basic idea, upon which he elaborates in this TED talk, is that you, the writer of the story, construct an elaborate mystery which causes the audience to ask questions. You construct figurative or, quite commonly, real impenetrable barriers in the story — an opaque "box" — and don't show what's inside the box, and then you make it really important to know what's inside the box. A few great examples are:

the locked hatch in the first season of Lost

the purpose of the works of Milo Rambaldi in Alias

Rey's parentage in The Force Awakens

Snoke's identity and origins in The Force Awakens

Having constructed this mystery, you, the writer, then:

do everything possible to avoid constraining solutions to the mystery, don't tell anybody what the solution is, do not create a solution at all, and finally quit the project.

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I could just stop writing there, and you would have a fairly decent impression of the Abramsian mystery box experience.

A mystery box is, in short, deliberate vagueness, to the point where even the writer doesn't know what's actually going on and has no intention of working it out, placed at the core of the story.

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Not every unanswered question in a story is a mystery, and not every mystery is a mystery box. Specifically, I want to make it very clear that a mystery box is a totally distinct storytelling device from a MacGuffin.

A MacGuffin is a story element, most likely a physical object, whose existence drives the story forward but whose specific nature is not directly relevant to the story. The MacGuffin is the diamonds or the secret blueprints or the microfilm or the antidote. A thing to remember is that the MacGuffin's nature is primarily irrelevant to you as a writer. This is because you are using the MacGuffin to drive your characters into places and situations where you want them to be, because of the story you are trying to tell. You would cheerfully swap one MacGuffin out for a different one if it better suited your purposes. The story is not about diamonds.

The nature of the MacGuffin is, however, of paramount importance to the characters in the story. Obviously: because if the MacGuffin had no particular nature then they would not particularly care about it.

And, separately, the nature of the MacGuffin may or may not be important to us, the audience. In some cases it is very important, because without understanding what the characters want, we can't get a firm grip on why they want it, we don't know what the consequences will be for them if they get it, and so we have a hard time understanding their motivations and behaviour.

But in many other cases it is not important to the audience what the MacGuffin is. All we need to understand is that someone wants the MacGuffin, and this is motivation enough. A fine example from J. J. Abrams' other work: the Rabbit's Foot in Mission: Impossible III. In cases like this, you, the writer, need to make sure that it is clear that we, the audience, do not need to know the MacGuffin's specific nature. Steps need to be taken to specifically dispel this mystery and move our focus away from that mystery and back to where it needs to be — on the complexity of the heist surrounding it and the interplay of the characters attempting to steal it. One way to do this is to simply have one character state outright that the MacGuffin's nature is not important. This is on-the-nose, but not ineffective.

You do this, by the way, because you don't want the viewer to dwell on the wrong thing; because you don't want to distract from the story. You don't do this

because identifying the MacGuffin would break the story, or because it is logically impossible for the MacGuffin to be anything, or because you, the writer, have no good ideas for what the MacGuffin is.

I mean, you can not know what the MacGuffin is. This is, at minimum, hazardous, because possibilities 1 and 2 can slip in, but you can get away with it. But I hope the chain of causality is clear here. You don't do this out of laziness or to hide your lack of imagination. You do it because, provided the audience's attention is effectively directed elsewhere, there's no need to do it... and if pushed, you probably have two or three ideas for what it could be, none of them particularly Earth-shattering.

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Why bring MacGuffins up if mystery boxes are totally different? They have some passing similarities and one crucial difference. As with a MacGuffin, the nature of the contents of the mystery box is irrelevant to you as a writer. The box remains sealed for the full duration of the story — or at least for the part of the story for which you are responsible.

As with a MacGuffin, the nature of the contents of the mystery box is hugely important to the characters. They do not know what it is, but their need to know is a critical driving force.

And, as with some (but not all) MacGuffins, you are not under any hard narrative requirement to come up with a concrete answer to the question. Although, in my opinion today (ask me again tomorrow), you probably should.

This is fine. All of this is fine! MacGuffins are fine.

The problem with a mystery box is that instead of dispelling the questions and focusing the story back on what matters, you deliberately run in the opposite direction. You focus the story on the empty box.

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There are plenty of excellent reasons why you'd use a mystery box. A mystery box is a great way to drive audience engagement in a story which is likely to run for a long period of time before it reaches its conclusion — perhaps years, or perhaps never. Asking a really good question and providing no answer prompts the audience to invent their own answers and share them. That's a conversation. That's social media and fan theories. That's great!

(And by the way, it does have to be a good question. Making anybody care about any particular thing in your story certainly still requires skill. A mystery box does not bypass this skill requirement, and Abrams certainly has it in spades. For that, credit is definitely due.)

You get to leverage the audience's collective imagination. A mystery box is like a blank piece of paper, a "catalyst for imagination" (Abrams' words) which "needs to be filled with something fantastic" (Abrams' words). We will, and we do, fill that blank paper, and you as the creator of the mystery get to take some of credit for giving us that imaginative spark, and for the profound inventiveness of our solutions, and for our vigorous fandom. Maybe.

A mystery box is an effective way to get the audience into the characters' head space. We want to know what the answer is. They want to know what the answer is. We are instantly on the same team.

The fact that the mystery box is empty is extremely handy because it ensures that nobody can guess the ending ahead of time. Just keep tabs on the fan theories and you can stay way out in front of them. If you do have any particular plans in mind, and somebody gets close, throw out your plan and throw a new element into the story which voids that possibility. If asked directly whether a theory is correct, say no. By definition, it can't be correct — because it was asked. And because there is no solution. Relatedly, a mystery box makes it very difficult for anybody involved in the production to leak the ending.

And finally, obviously, a mystery box saves you some (but not all) of the work of constructing the story in the first place. You have a solid beginning, you have some sketch ideas for the middle, and... you're done. This is an especially efficient use of your time if your project is, for example, a television show with a strong possibility of being cancelled before it goes anywhere, or the first film in an ongoing franchise.

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Why not use a mystery box?

A mystery box weaponises your inability to tell a complete story.

A MacGuffin may be a technically missing piece to your story, but when properly used, our attention is diverted to more important things. A mystery box focuses all of our attention on your failure.

This is extremely dangerous if the story ever reaches its end, because it is intensely frustrating for a story to be missing its ending or to have a dissatisfying ending. Some will argue that in many stories, the journey is more important than the destination. Well, sometimes. Personally, I like a story to have a well-defined ending point, and closure, and finality, but not every story is written for me, and that's fine. Sometimes the journey really is the point.

But this is never true of a mystery box. A mystery box sets itself up as important. It transfers our focus onto it. It promises a payoff, and the payoff is the reason we invest our attention and speculation. For there to be none is inexcusable.

The end of the first season of Lost: after lengthy tribulations and conflict, after much struggle and mystery, the hatch is finally opened.

The end!

See you next year!

Do you think we'll have an answer by then? Do you feel like spending another whole year speculating what's inside the hatch? Do you think we'll have come up with a better idea than "another mystery box"? What happens when the countdown runs out? Mysterious sigils now?

But it's a problem even before the end. Withholding information is not the same thing as not having information. Audiences can tell when something is structureless, baseless. Stories with well-defined endpoints in mind are angled towards that endpoint in all sorts of tiny ways, ways which we pick up on. When there's a consistent direction to a story, small details hang together behind the scenes. And when they don't add up, we can tell the difference between an honest continuity error and someone making things up as they go and, if they're even taking notes — which we sure are — deliberately ignoring them.

We get a sensation of whether a story is going somewhere or going nowhere. A mystery box story states clearly, up front: you don't know where you're going with this. You may be going nowhere. You don't care.

A mystery box represents infinite possibilities, but it commits to none of these possibilities. It isn't the sum of those possibilities. It's still empty.

Many people won't share my opinion on this next point, but: Yes, a mystery unlocks all the power of my imagination. I can write a story for you, if you like. Maybe even a better one! But I'm not here to explore my imagination. Your imagination has given me a blank sheet of paper? I already have blank paper. I have plenty to say. I probably committed to your story because I was interested in what you had to say. I'm here to explore your imagination.

Actually, scrap that. Imagination is overrated. Anybody can have an idea. I'm here to explore your ability to execute. A mystery box is a confession that you can't.

(I'm sorry that I wrote all this addressing the bad writer as the second person. This would have been better a few hundred years ago using "one" instead of "you" throughout. This isn't personal. Your writing is great.)

Finally, a mystery box offloads your responsibility for figuring out the ending to other writers. You deliberately opted out of a necessary piece of work because you couldn't or wouldn't do it. By doing this you made the job harder for the person or people who did. Although you may have worked hard to leave the door open for many possible solutions, it's likely that there is no solution at all which retroactively makes literal or thematic sense out of everything which went before. I would characterise this as, well, unprofessional. Rude, even.

This is your last chance to stop reading before I go into specifics about The Last Jedi.

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We don't know who Rey's parents were. They abandoned her on Jakku and she's been waiting her whole life for them to come back. Who could they possibly be? What could possibly happen when she meets them again? Textbook mystery box.

I've been watching J. J. Abrams do this stuff for a while now and although I didn't encounter the term "mystery box" until relatively recently it was abundantly clear: at the time that The Force Awakens was made, this box was one hundred percent empty. It was hard vacuum. A core directive in the production of that film was undoubtedly "Do not, do not, do not tie our hands for Episode VIII." There was no particular grand revelation in mind. Or rather, every possible grand revelation was under simultaneous consideration.

There were two major possibilities for who Rey's parents could be. They were going to be people we already knew, or people we didn't. Star Wars has had a mystery of this kind once before, at the end of The Empire Strikes Back when Yoda reveals that Luke Skywalker is not the Jedi's last hope, "There is another". Now, for me to say that any particular thing was "originally intended" in Star Wars is generally misleading; Star Wars as a plan evolved hugely over time, as is very well-documented. But it is known that at at least one point during the production of Empire it was intended that Yoda would be referring to a new character, who would be introduced in Episode VI.

In the final analysis it worked out to be Leia, who also worked out to be Luke's sister. This was simultaneously one of the more boneheaded possible solutions to that problem and one of the more boneheaded possible resolutions to the Luke/Leia/Han love triangle. It was the wrong answer in Return Of The Jedi, and it would have been the wrong answer for The Last Jedi. The Star Wars universe would have imploded due to a shortage of characters and a lack of scope. Rey's parents could not be people we already knew.

That still left infinite possibilities. Rey's parents could have been new characters. All of Episode VIII could have revolved around them, ramping up to a climactic, dramatic reunion. Anything could have happened. That's the intended power of the mystery box.

But in the final analysis, in The Last Jedi, Rey's parents are nobodies. They are dead. We never see them. She is no one. She comes from nowhere.

It's actually an extremely good moment. It doesn't happen in a vacuum; far from being a let-down, it explains the known facts, it ties off a thread and it expertly sets up what happens next in the story. I think it was probably the best possible resolution to that mystery, and I was impressed. I call that skill by Rian Johnson, and a lucky break for J. J. Abrams.

As a slightly less ambiguous example: Snoke. Who is he? Where's he from? We've never even seen him in person. Does he really look like that? Is he really that tall? Is he someone else, someone we already know, using a holographic disguise? Palpatine? Darth Plagueis? Luke Skywalker? Maz Kanata? Classic mystery box.

In The Last Jedi, it turns out that he is normal-sized, he really looks like that, and nobody cares. The information proves not to be germane to the story at hand, and the character himself is removed from the saga. It is, frankly, a tremendous relief.

(The Last Jedi is a lop-sided, confused, frustratingly-paced film with one or two moments of pure open-mouthed awe and more than two dozen moments of Prequel Trilogy-level inexplicability. Axeing the mystery box stuff was one of the better decisions made in it.)

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These are the best case scenario endings for a mystery box story. Somebody who knows what they're doing comes along; with minimal ceremony, they open it; we see what's inside; then they stomp the box flat, put it in the recycling and move forward with the story.

And I put it to you that if the best possible thing that could be in your mystery box is nothing at all, there is definitely, definitely a better way to tell your story.

I see that Abrams is back for Episode IX. It might be good.