In a busy lobby of the UN building in New York, advertising executive Roger O. Thornhill finds himself holding a knife over a dying man who has just been stabbed. A woman screams and all eyes turn to witness him in flagrante delicto. A newspaper photographer just happens to be there to capture the incriminating moment. Thornhill is the wrong man but there’s no way he can explain, so he runs. In order to clear his name he must discover who the villains are and what they are up to.  ​ If you haven’t seen North by Northwest at, you might expect from that synopsis that a key moment in the picture would be the revelation of the villains’ activities. After all, it is the reason why our hero is chased, drugged, shot at, arrested and cropdusted during the ensuing two hours of action. As the cause for all this perilous adventure, it must be important. Surely. But you’d be wrong. It’s just the MacGuffin.  ​ Hitchcock gave the name MacGuffin to the villain’s objective in a spy or crime story. This desired object is the spring that releases the elaborate mechanism of the plot. In some thrillers, it is the rocket fuel formula or the plans of the new submarine; in others it might be the holy relic, or the blue diamond, or the jade statuette that is the national treasure of the mountain kingdom of Farsbanistan. The criminals want it desperately and our heroes get in the way of their attaining it. But, as Hitchcock realised early in his suspense career, to the audience it hardly matters at all. The director only need stress that this thing, whatever it is, matters greatly to the characters, and away you go.  ​ Why is it called a MacGuffin? Well, there is a story attached to the name that Hitchcock liked to repeat, but it doesn’t make things much clearer.  Two strangers are in a train compartment, and one asks the other what he has in the strange box in the luggage rack.  ​ ‘That’s just a MacGuffin,’ the other explains. ‘What’s a MacGuffin?’ he asks. ‘It’s a device for trapping lions on the highlands of Scotland.’ ‘But there aren’t any lions on the highlands.’ ‘In that case, that isn’t a MacGuffin.’  ​ The point of this story – one supposes – is that the first man should just mind his own business; the details do not concern him. Similarly, it isn’t the business of the audience to know precisely what the secret plans are. Because, as Hitchcock realised, once the audience is absorbed in the action, they won’t care. They have paid good money to be thrilled by the chase, not hear a lecture on the chemical make-up of rocket fuel or the convoluted backstory of the Tequila Mockingbird.  ​ For this reason, vagueness is the distinguishing feature of a film MacGuffin and most MacGuffins retain their mystery to the end. Hitchcock was particularly pleased with the MacGuffin in North by Northwest, whose vagueness is emphasised in the movie with a joke. Escorting Thornhill to the plane, the government counter-intelligence chief, called the Professor, fills him in on the villain Vandamm. ‘He is an importer and exporter of government secrets,’ he begins, but his further elaboration is drowned out for the audience by the plane’s roaring engine. Hitchcock later told François Truffaut in an interview that it was ‘my best MacGuffin, and by that I mean the emptiest, the most non-existent, and the most absurd.’Itisonlyinthefinalmomentsofthefilmthat a pre- Columbian figurine falls to the floor and, in the briefest of cutaways, we see microfilm spool out from its hollow insides. But what is on the microfilm? We are never told. And who cares? It just the MacGuffin.