Here’s a joke told by Emo Philips about his childhood:
When I was ten, my family moved to Downers Grove, Illinois. When I was twelve, I found them.
Right up until the punchline of “I found them”, the information provided by the set-up seems perfectly normal and straightforward. What we learn at the punchline is that we have completely misunderstood the information that’s been given to us (a misunderstanding based upon an ambiguity within the phrase “my family”). The Emo on stage, telling the joke, has a “correct” understanding of events from the start to the finish of the joke. At the end of the joke, we’ve abandoned our original misapprehension and joined Emo in “correctly” understanding what really happened. We’ve caught up with the comic, who has spent the whole of the set-up being (secretly) better informed.
A certain amount of mental energy has to be expended in reframing the narrative to fit the newly revealed facts. We have to go back and re-assess what we’ve been told, and we have a complex awakening, which includes a factual realisation (Emo’s family abandoned him when he was ten and it took him two years to find them) and a kind of existential realisation (we’ve been tricked by the set-up into thinking Emo was telling us one thing, when in fact he was telling us something entirely different).
This realisation that we’ve been tricked is similar to the feeling you get at the end of an Agatha Christie novel when the murderer is revealed and you realise you had all the facts in front of you all along, but hadn’t grasped their significance. The experience of reading one of Christie’s books is here described by devoted fan Mary Webb, who runs website the all-about-agatha-christie.com:
I have often reached the end of one my Agatha Christie novels and then searched my way through the book again to identify the pointers that I had missed but which Hercule Poirot or Miss Marple seized upon straight away.
In a way, the young Emo character within the joke is the detective, beginning the joke in ignorance, ending it by solving the mystery of his family’s disappearance. Emo ends the joke, aged 12, with the same complete knowledge of events that the Emo on stage had all along. We, the audience, go through a rather faster learning curve.
In novel after novel, Agatha Christie tricks her reader. As Mary Webb says:
…the reader will inevitably be lulled into a false sense of security, believing themselves to be on the right track, only to discover that yet again, the Queen of Crime has led them up the garden path.
This is the same modus operandi (albeit on a larger scale) of a stand-up comic who tells one-liners and keeps tricking the audience into believing set-up after set-up, lulling them into “a false sense of security”, time and time again. The set-up contains the “clues” to a complete appreciation of events that the punchline reveals.
The only real difference is timing. Where Agatha Christie has to keep the wool pulled over her readers’ eyes for a whole book, Emo Philips has to do it for the duration of a sentence. Part of what makes the joke funny is the intense compression of the narrative. The joke could probably be expanded to book-length, with detail after appalling detail padding out the bare bones — the desperate young boy searching Illinois for his vanished family — but the comedy would melt away into tragedy.