Mackenzie Casper is a brilliant student. But she is best known for her mother, a best-selling author whose dark, twisted thrillers have a dedicated worldwide fanbase. When her mother dies in an accident, fans across the world are left grieving, and the investigators are asking: Was that really an accident?

The day of the memorial service, Mackenzie gets the first mysterious envelope, signed,

From #1 fan. XOXO.

Inside are the pages of her mother’s diary that start with the lines:

Want to know a secret?

Love, Mom.

What Mackenzie reads leaves her in shock.

Then comes the second letter.