One of the hardest things about recovery is coming to terms with the fact that you can’t trust your brain anymore.
-- Mallory as narrator (chapter 1)

Importance: The quote establishes that Mallory may not be a completely reliable narrator. It shows that Mallory is aware of not always being able to trust herself. It allows the reader to see Mallory honestly within the limitations Mallory knows about herself.

There is no rest of the story. After Annie died – or went missing, who knows – her family turned the cottage into a garden shed. Wouldn’t let anyone stay out there. And it’s been that way ever since, seventy-some years. Until this month.
-- Mitzi (chapter 4)

Importance: The quote gives the reader insight to an unsolved crime and mystery at the Maxwell home. It establishes that the place where Mallory is staying is unsettled, similar to how Mallory feels in her new job.

It’s a picture of a man...
-- Mallory as narrator (chapter 5)