Most writers set up a series of reveals that build steadily. M. Night Shyamalan sets up his structure to play one monster reveal. This reveal isn't just the biggest reveal in the story so far. It is information that is so powerful it changes everything that has come before. It is like an earthquake underneath the world the audience shares with the hero.
Most writers do not use this technique because you have to come up with a second alternative for how the events of the world work and what they mean. You have to be able to come up with a detailed reality with the same apparent events as the first alternative, but whose cause-and-effect connection is totally different.
Most writers have tremendous difficulty coming up with one cause-and-effect line. But in Sixth Sense Shyamalan showed that if you can come up with two, you can blow the audience away.
