What do directors seek to establish in the openings of thrillers?

Thriller openings aim to establish important elements in the film such as tone or mood, the location and the characters. 

Tone/Mood

The disappearance of Alice Creed establishes the tone with the intense music in the first scene. The music makes fairly normal things, such as shopping, suspicious and establishes a dark tone for the film and creates a sense of foreboding. The music builds up the audience with anticipation which is reinforced by the constantly moving camera. The panning camera is used to reveal important items or actions in the shot, such as the part where the camera pans over a row of parked cars to reveal the two characters breaking into a van, or the part where the camera pans over a set of items being packed and reveals each item as worse than the other items already revealed. The camera is slow and smooth which adds to the anticipation the audience is already feeling from the music, which slowly gets more intense as the scene moves forward and things are revealed such as the intent of the two characters in the scene.

Shallow focus is used in different parts of the opening scene of The disappearance of Alice Creed especially when the characters are doing seemingly normal things, the shallow focus makes whatever the characters are doing seem sinister and suspicious. This is reinforced by the music in the scene which also makes the characters and their actions seem suspicious.

Characters

The film Se7en successfully establishes the character of detective Somerset in the first scene. I uses light, space and props to make the character seem isolated and brings up questions about his past. Metaphorical space is used to imply that the character used to have someone in his life and misses them, which is reinforced by a prop in a different shot. This shot is successful in establishing his character through the different props and their meanings to the character and implications to the audience. For example, the badge tells us that the character works for the law which is shown in the scene again as the director establishes him as a detective through the use of a classic costume, which is a convention of film noir. The gun could connote violence and could foreshadow events later in the film, which is reinforced by the knife which also shows that he is paranoid or wishes for control which is reinforced by the precision and neatness of the placement of the items in the shot. The pen show preparedness and reinforces the implication that the character wants more control in his life.

Similarly, the film Double Indemnity uses costume to establish the character in the opening scene, but for a different effect, the character wears a classic costume but it is used in a way to obscure most of his face and body to make him look suspicious and to imply that he has a dark side. This is reinforced by the director's use of long shadows and darkness, a convention of film nior, especially in this shot. This shot could be breaking the rule of thirds as well as the character has been pushed very far to the left, and left is sometimes associated with evil or badness, which could reinforce the idea that the character has a dark side. Later in the opening scene, another character is well established as a femme fatale, which is another convention of film noir.

Location

The Third Man establishes the location of Vienna in the opening scene with shots of grand interiors with banisters that create long shadows, disorienting leading lines and geometric shapes. The disorientation links to the chaos of the war and the effects of the war in the post-war period in Vienna. This shot reflects Vienna at this time as the lines lead out of the frame, creating a disorienting shot which is reinforced by the dutch angle used here and the long shadows create unusual shapes, which all create connotations of chaos and help establish the location and the mood of the location at the time.