The Outdoor Girls at Ocean View

The Outdoor Girls and their friends vacation at Ocean View with Betty Nelson and her mother. After Amy Blackford learns that pirates sailed the waters near Ocean View, she becomes obsessed with the idea of finding pirate treasure. Amy is delighted when the girls dig up an old box that is buried on the beach.

The box does indeed contain treasure-a fortune in diamonds! The box also contains a queer cipher, which the young people immediately attempt to decode. Their efforts prove fruitless, and they wonder whether the diamonds were smuggled into the country.