Case of the Boat Bomber

Why did someone blow up Billie Bob's rebuilt riverboat? That's the latest case Em and Sandy are asked to solve. How is that related to a yacht that was sunk two years ago off the coast of San Lucas or the apparent accidental death of a big time crook's ex-wife? There doesn't seem to be anything relating these three incidents until the bomb signatures match up.

With their friend Stephanie, the girls fly to San Francisco for a vacation and also to look into the business dealings of Tom Everest...