Lydia is dead. But they don't know this yet. 1977, May 3, six thirty in the morning, no one knows anything but this innocuous fact: Lydia is late for breakfast.
-- Narrator (Chapter 1 paragraph 1)

Importance: The title of the novel, "Everything I Never Told You," hints at one of the major themes of the book: keeping secrets. By opening her novel with "Lydia is dead. But they don't know this yet" Ng welcomes the reader into that world by giving the reader knowledge the characters do not have. This also indicates a certain level of trust the reader should place in the narrator; because the narrator is all-knowing, he or she will be able to dispense privileged information as the story requires. Furthermore, by mentioning Lydia in the first sentence the narrator makes it clear that Lydia is one of if not the most central character.

How had it begun? Like everything: with mothers and fathers. Because...
-- Narrator (Chapter 2 paragraph 1)