There is no needless information in a story: if a character keeps a gun under his pillow, you can bet it’s going to be fired by the end of the story. Or, at least, it should be, according to Chekhov’s Gun.

This principle, named after Russian playwright Anton Chekhov, argues that every detail in a narrative should have a purpose, like the rifle in his own play "The Seagull", the baseball bat in "Signs," and that sneaky Rita Hayworth poster in "Shawshank Redemption." However, not all authors agree.

Ernest Hemingway, for example, preferred his details like a good cocktail: sometimes just for flavour. So, if Hemingway puts a gun under a pillow, maybe it's just because the character couldn't find a better place to stash it.