Guns on the Wall
 
There's a famous saying by the Russian author and playwright Anton Chekhov, which goes: 'If you hang a gun on the wall in Act I, you must use it in Act III.' Sometimes it's differently translated as: 'If you introduce a gun at the beginning of the play, you must use it by the end of the play.'
 
J.K. Rowling hangs plenty of gun-equivalents on the walls of Hogwarts and elsewhere, but Chekhov's rule needs to be taken with a large pinch of salt when we're talking about novels. What he had in mind was the script of a play, where anything that's important enough to be mentioned in the stage directions should have its part in the action. Suppose, though, that in such-and-such a scene set in a stately home, that gun on the wall of the stage-set wasn't in the play script but is just a touch of high-class decoration added by the set designer…?
 
Harry's Uncle Vernon actually does buy a gun in Chapter Three of Philosopher's Stone--but it's not there to be used, only to underline how desperate he's getting (and also, when Hagrid so easily takes it away from him, to remind us again of what a wimp Vernon really is). It's an extra touch of make-up or stage decor, rather than an important piece of plot machinery.
 
Part of the fun of reading detective stories is the challenge of trying to sort out these ornamental extras from the real 'guns on the wall', the clues which are part of Agatha Christie's or Dorothy Sayers' or J.K. Rowling's secret script. As her readers have discovered, Rowling is rather good at inventing smokescreens of comic diversion to help conceal important clues, even when they're right under our noses. Now you see it, now you don't.
 
Chocolate Frog
 
In Philosopher's Stone, our author wants to plant the name of Nicolas Flamel--the wizard who created the Stone itself--in such a way that we barely notice its appearance, and will later kick ourselves for not remembering it. So the brief mention of Flamel is deftly slipped into a mini-biography of Albus Dumbledore, printed on the back of the collectable picture card which Harry finds in his very fi rst Chocolate Frog wrapper.
 
Meanwhile, during this scene on the Hogwarts Express, there's a flood of distraction as Harry boggles at new wonders of the wizarding world. It's the first time he's met photographs whose subjects wander in and out of the visible picture-frame, and it's also his first encounter with half a dozen other brands of magical sweeties like the very weird Bertie Bott's Every Flavour Beans. A subtler distraction for the reader is the nagging thought that perhaps Chocolate Frogs are a little homage to the Crunchy Frog sketch from Monty Python's Flying Circus--whose Cockroach Clusters will indeed turn up much later, in the third Harry Potter adventure...

 

All this inventive stuff is great fun, and it is also a conjuror's display of dazzling lights and coloured ribbons, designed to lure your eye away from the key reference to Nicolas Flamel. Rowling has a real gift for this kind of misdirection, as perfected by stage magicians who subtly guide you to look in just the wrong place.
 
Pyrotechnics
 
Onwards! A bit closer to a literal gun, since they contain real explosive, are the Filibuster Fireworks which appear early in Chamber of Secrets. At first sight these don't appear to be at all important--just something to provide entertainment for young wizards and witches, like all those weird sweets. But by writing these fireworks into the story, Rowling is secretly preparing a stage-effect for a much later chapter. When Harry needs to cause a diversion in the Potions class, tossing a Filibuster Firework into a Slytherin student's cauldron is a perfect way to create total chaos.
 
Why are they called Filibuster Fireworks, anyway? The most common meaning of 'filibuster' is to make long, long speeches in Parliament or Congress, not to convince anyone of anything, but to waste time and prevent unwanted laws from being passed. It's a tactic of diversion and delay--which, of course, is exactly how Harry uses his firework.
 
Magical Misfires
 
The most obvious 'gun on the wall' in Chamber of Secrets is Ron Weasley's wand, which gets broken early in the book when the flying car crashes into the Whomping Willow. As a result, the Spellotape-repaired* wand becomes a totally unreliable weapon. Ron tries to curse Malfoy, and the wand backfires, leaving Ron himself burping up great masses of slimy slugs for the rest of the day.
 
As well as being good entertainment in itself, this magic-gone-wrong comedy lays the groundwork for a much more serious miscarriage of magic. Near the end, Gilderoy Lockhart himself tries to wipe out Harry's and Ron's knowledge that he's a posturing fraud. But it's the broken wand that he grabs, and his Memory Charm bounces straight back at him. The 'gun on the wall' has gone off at last, and--as neatly foreshadowed by those slugs--it backfired.
 
An interesting side-question: could Lockhart really have got away with it if he'd succeeded in wiping out the boys' memories? This isn't some remote village in Transylvania or Tibet, but Hogwarts School, where Madam Pomfrey and Dumbledore would work their hardest to cure a couple of dazed and blank-minded pupils. As Voldemort himself knows, and mentions when talking to Wormtail early in Goblet of Fire, the effect of a Memory Charm can be broken by an expert wizard. The most likely explanation is that Lockhart was too ignorant of the higher branches of magic to know this important fact.
 
Putting Back the Clock
 
The little mystery of Hermione's classes, and how on Earth she manages to attend more than one at the same time, runs through the action of Prisoner of Azkaban. Is she using some special charm that allows her to split into two or even three Hermiones, all of whom can go to lessons or take exams simultaneously?
 
Eventually all this bafflement is explained by the Time-Turner which Professor McGonagall has persuaded the Ministry of Magic to loan to Hermione. Now, with special permission from Dumbledore himself, Harry and his closest friends can save the day by going back in time to do all the things they didn't achieve in the three hours that had just gone by. If such an amazing gadget had simply appeared when needed, this would have been a totally unconvincing way to save the book's plot. What makes it satisfying is that the Time-Turner's effect on Hermione's timetable has been a running joke, and a source of mild bewilderment, ever since we first found her planning to take three classes at once in Chapter Six.
 
The Time-Turner is such a powerful plot device, capable of solving so many problems, that Rowling later takes some care to rule out its further use, as we'll see in the chapter 'Awkward Consequences'.
 
Key to Transport
 
The introduction of the Portkey in Goblet of Fire is much more straightforward. It's not a mystery, but just a useful part of the vast magical crowd-control apparatus that's needed to organise the Quidditch World Cup in a country full of Muggles. As the 'port' in the name suggests, this device instantly transports or teleports anyone who's touching the key (the tip of a finger is enough) when its...