The Silence are a species of pale-skinned aliens with long thin faces and no mouths. All of them wear black suits, and they can gather together electrical energy to disintegrate anyone with their fingers. If you are not looking at one, or a picture or recording of a Silent, you will entirely forget that they are there, and the Silence have used this to manipulate human history so that the answer to the universe's oldest question of the Doctor's true name is never known.