Suspense/Shock.

Alfred Hitchcock famously draws a sharp distinction between shock and suspense. Shock occurs when a film confronts spectators with the unexpected rather suddenly, and thereby creates a momentary shock. 

Whereas suspense involves confronting them with what they know is coming in a prolonged way.

He also once famously explained the feeling by describing a bomb underneath a table. If the bomb explodes, the audience is given a shock. In a suspense film, however, the audience knows there’s a bomb underneath the table. It’s rigged to explode at noon and the clock is ticking. ‘In these conditions, the same innocuous conversation becomes fascinating because the public is participating in the scene,’ Hitchcock explained. ‘In the first case we have given the public fifteen seconds of surprise (shock) at the moment of the explosion. In the second, we have provided them with fifteen minutes of suspense.’

The suspenseful bomb analogy was depicted astutely in 'Sabotage'. In the film, Hitchcock has the saboteur's young brother-in-law unknowingly couriering a bomb. The boy is assigned to deliver a reel of film from one location to another, and he doesn’t know—while the audience does know—that a bomb exists in the film can. So we watch him go through his lengthy, banal commute while we are being totally suspended waiting for the bomb to go off. It ends tragically for the poor lad, but the lead-up to the inevitable explosion is increasingly harrowing because of these elements.

'Rope' (1948) is probably the best example of Hitchcockian suspense. In this explicit melodrama, Hitchcock has tried the trick of shooting full-length picture in one set and in one continuous scene. That is to say, he has made his camera a random observer in a suite of rooms in which a murder is being committed by two young men just as the picture begins. And he has kept his camera steadily turning upon the subsequent drama which occurs as guests arrive for a cocktail party and the murdered body lies concealed in a conspicuous chest. The suspense of the picture is not in the film itself, but merely in the method which Hitchcock has used to stretch the tension out for the length of the (perhaps slightly tedious) stunt, which ends up only ending in a fizzle. It's almost obvious from the beginning that they are going to be found out, however, because what would be a point in a film where no-one except the two men ever know and everything goes on as usual?