Dink, Josh, and Ruth Rose are having a great time visiting their friend Sammi, the prince of Costra. They swim, soak in the sun, and admire the bright yellow yacht that is moored just offshore. But the owners of the yacht are acting a little suspicious. And then there's a robbery on the island! Could there be a connection between the robbery and they mysterious yellow yacht? It's up to Dink, Josh, and Ruth Rose to find out.