Irony in screenwriting isn’t about the characters wisecracking in a dry and knowing way. Knowing is part of it, sure, but the knowing in question is the relationship between what the character knows and what the audience know. It’s a dance, and controlling it enables the writer to control pace and tension in the film effectively.

Thrillers in particular work according to who knows what, when. If an audience knows in advance that the sheriff the protagonist opens up to is allied with the bad guys, then everything the sheriff says and does will be loaded with that knowledge. In turn, that creates empathy for the protagonist’s predicament when the sheriff, say, offers to put the hero up in a cell for the night, to save him from his pursuers.

Writing in this manner calls for control of point of view at all times. Always seeing a story from the perspective of one character is one valid choice - others add fascinating complications. In the example just used, if the hero discovers the truth about the sheriff when, the morning after he accepts the offer to stay in the cell, the bad guys turn up, that’s one perfectly valid way of telling the story.

But imagine how much more tension can be wrung out of the situation if you know that the sheriff is in contact with the bad guys, acts sympathetically to the hero, and realises the financial payoff he can make by selling him to the villains. It turns the sheriff from a fairly bland character into one making important choices affecting the hero’s destiny, all the while as the hero accepts the sheriff’s friendship. You can twist it further still: what if the sheriff ultimately decides to side with the hero, even after he’s arranged to sell him to the bad guys? The story options multiply, as the hero is faced with the potential of eluding his pursuers, and he and the sheriff have to concoct a way of him getting away that leaves the sheriff looking as if he still sides with the bad guys.

And so on…The point here is that allowing your story to have several viewpoints allows you to increase the jeapordy of what’s happening in all kinds of interesting ways. And it doesn’t just apply to thrillers. How about a romcom? Let’s say the guy with the hots for the woman is told seconds before they converse for the first time that she despises men of his profession…That gives the scene a frisson it would otherwise have lacked, and reveals something about his character according to the way he responds to this news (does he lie about his job, or defend himself in a way that seems excessive?), just by adding a little piece of dialogue from a third party.

Or horror: a character has been bitten by a vampire, but thinks she won’t become one herself because there was just the one bite. Cut to another scene in which a priest says that vampire victims only become vampires themselves if the bite happened on a full moon, at which point the viewer remembers that the attack did indeed happen when the moon was full in the night sky. In that instance, the audience had the information all along, and it becomes knowledge only in the context of a later revelation.

Alfred Hitchcock was a master at parcelling out information to the audience to hook them into stories and empathise with or change their allegiances to different characters as the film went on. It’s a vital part of the screenwriter’s toolbox, and one which I believe is best learned by experimenting with different ways of approaching the same story. And if you can find a way of doing so that works with Hitchcock’s mastery, then I want to see your script reach the screen.