Intertextuality is when we take inspiration from other people's work and use it for our own.
When transferred to the film industry, directors take camera angles, mise en scene and settings from other films and use it in their own. This creates the conventions within genre as most films will borrow techniques. In the thriller genre, lots of techniques are taken from the film 'Phsyco,' a 1960's classic directed by Alfred Hitchcock.
There is a very famous sequence in the film that takes place in a bathroom, where a girl is showering. The bathroom is all white, which is also seen in many other films as it connotes the innocence of the victim. The figure enters the bathroom, and this is seen by the audience through the transparent shower curtain. However the girl is oblivious as her back is turned away from the door. The dramatic irony at this part has a maximum impact of tension.
When the victim is attacked, loud and fast paced music alerts the audience, this is just one of the ways directors use music to forbose the future events in a film. When she is killed she collapses in the bath. As she falls, she takes hold of a shower curtain, and there is a close up on each circle popping out of the rail. This was also seen in the stepfather.
The close up of blood dripping down the plug hole is also particularly thrilling as it emphasises the horrific thing that has just happening without showing too much. This in my opinion is an effective way
And finally, the closeup on the eye, zoomed out to reveal the rest of the scene.