Twelve-year-old BFF’s Ginnie and Tillie, want to be sisters. Tillie's divorced mom plus Ginnie's widowed dad could equal a lifetime of round-the-clock girl talk and slumber parties. Too bad Dad vowed to never marry again. Ginnie and Tillie form a secret club. They come up with the perfect mission to change his mind: ‘Operation Secret Sisters.’

Before long, Tillie seems happier about gaining a dad than a sister. Ginnie suspects Tillie has turned ‘Operation Secret Sisters’ into a scam called ‘Operation Steal My Dad.’ Things get more complicated when Ginnie stumbles across her real mom’s hidden journals. Ginnie can finally get to know the mother she doesn’t remember and Dad doesn’t talk about.

When Dad discovers she has the journals, he takes them away. Ginnie needs to figure out what the big mystery is before her relationship with her father and her best friend are ruined forever.