Valentine's Day is approaching and everyone seems to be crazed with love—except for Mallory. She's been invited to a Valentine's party next door and rumor has it that her next-door neighbor's dad is going to propose to her best friend's mom. What will it mean if her two best friends become brother and sister? Where will she fit in? And to make matters even more confusing, Mallory is receiving presents from a secret admirer. Who could it be? Mallory feels like everything is changing and she has lots of questions about life, love, and friendship. Since her two best friends are preoccupied, Mallory turns to her diary to find the answers.