What "They Might Be Giants" Taught Me About Writing

So.  They Might Be Giants is about a delusional former lawyer (George C Scott) who believes he's Sherlock Holmes.  He follows clues in a manic fashion, like Batman in the old TV show, interpreting a thrown-away bag with the words "Back to School" on it as a sign that he needs to look for a school run by someone named "Bagg."  That sort of thing.  He can't seem to accept that the evil and cruelty peppering our lives is just random happenstance, but thinks it must be the result of an evil genius, a foe worthy of attack: ie, Moriarty.  You can't mistake that Moriarty is Satan, a principality terrible in both senses of the word, a being of pure malevolence, but not without a sort of grandeur.  And Holmes is a bit of a Christ figure - seemingly healing everything he touches, and asking at one point of self-doubt, "Who do you think I am?" a question Jesus put to disciples and Pharisees alike.
Holmes falls under the treatment of a psychiatrist named - wait for it - Dr. Watson - played by Joanne Woodward.  He draws her into his delusional world, and they set off on a series of escapades, silly but fraught with deeper meaning, blah blah blah.
It's the ending I want to talk about.

At the end, Holmes and Watson are staring into a black tunnel late at night, awaiting the appearance of Moriarty himself.  Holmes says he sees him, and stands, "Not on my knees," he says.  Watson (Woodward) is still kneeling, and cries that she can't see or hear anything.  The film cuts to the tunnel, still dark and empty as a skull's eye socket.  Holmes tells Watson to stand, which she does, still mourning that she sees nothing.  She wants to believe.  Then she says she can hear Moriarty.  We hear it too, hoof beats.  Back to the tunnel, as dark and empty as before.  Holmes points, can you see him?  Can you see him?  And Watson responds in fear, hope, and love that she can.  At this point they hold hands and the credits roll.  The audience has seen nothing but an empty tunnel and heard hoof beats that may be imaginary or may just be an ordinary person approaching on horseback.  (The location is a riding school, I forgot to mention.)
Why is this ending so important to me?
Let's start by noting that audiences, whether they be readers or viewers, are half-sold on fantasy already.  Coleridge called it the willing suspension of disbelief, but it's stronger than that.  It's a positive appetite for belief.  We know we're about to be lied to, we go in expecting to be lied to, wanting to be lied to, and are only disappointed if the lie isn't a good one.  We know Huck Finn and Humbert Humbert don't exist.  So convincing the audience of a lie isn't much of a trick, the audience arrives pre-convinced.
It gets just a little bit tricky when you wink at the audience and say maybe I'm lying, maybe I'm not.  Is there such a place as Oz, or is it only Dorothy's dream?  In literature, no one I know of plays this game better than Nabokov, but I'm going to stick with movies because that's what I started with.
Here's some movies that play a little bit of is-this-a-lie or is-it-not legerdemain: The Sting, The Wizard of Oz, The In-Laws, The Gods Must Be Crazy, and They Might Be Giants.  I have arranged them in ascending order of how well I judge they handle this delicate conjuring trick.
First of all, The Sting.  It is a fun movie, but the ending is a flat cheat.  We discover that the director has deliberately lied to us about what was going on, that in a movie about con-artists and patsies, the ultimate patsy was the audience itself.  We don't care, though, because we have been so thoroughly charmed by Newman and Redford; like any great confidence trick, afterwards we don't even blame the guys who rooked us.
The Wizard of Oz is another cheat; Dorothy has these wonderful adventures, wakes up and - it was all a dream. Again, the film is so delightful we don't mind, and besides, the dream is true for Dorothy, and there is something genuine gained.  (A lesser film maker would have included some incongruous bit of corroborative detail, a red sequin from the ruby slippers, say, to make us wonder if it were really a dream, but that would just be muddying the issue.)
Then we have The In-Laws, which is entertaining, neither as great as Oz or Gods, but has the upper hand in that it is a good, honest, straight-forward lie, instead of an outright flim-flam or a dream.  A lot of stories fall into this range, for example, The Sixth Sense or Rear Window.  Basically, it works like this - there's a character who says something that is palpable nonsense - I'm a CIA agent, there's a giant gelatinous blob eating the town, the next door neighbor is a killer.  And then, it turns out, a wonderful thing! the lie is true after all.  The liar turns out to be a truth-teller, the fool a wise man, and the lunatic sane.

With The Gods Must Be Crazy, we enter into the higher realms of epistemology and metaphysics.  In one of the interwoven stories Xi the bushman must find the end of the world to throw away a coke bottle.  The audience sitting in the air-conditioned theater eating greasy popcorn and iced soda, so totally disbelieves the world has an end it doesn't give it a second thought, but then - at the end of the movie - Xi arrives at the edge of the world!  We instantly reconcile ourselves that what Xi is standing at a cliff, so misty below that he can't see the other side, or whatever valley or sea is below, but to Xi, it is a the end of the world and he is satisfied and so are we, in a deliciously dissatisfied way.  For Xi, his lie is true, but we are left to see that our own truths are the lies we happen to believe, lies that may not be as beautiful or profound as Xi's.
Finally They Might Be Giants.  I ask you to refer back to the ending of the movie as already described.  The point is that the audience knows it is not Moriarty.  We are left in the position of Joanne Woodward before she rises to her feet - wanting to believe, hoping to believe, but still suffering disbelief, envious and wanting to join the lucky ones who do believe, and still hoping we will believe.
If you can bring your audience to that precise edge, where they hunger to believe the lie even as they still know it is a lie, not one step further nor one step back, you have done something rare indeed.  And something worth doing.