The finders-keepers rule

"Maryellen takes a break from practicing for the big Rock Around the Clock dance to go to the beach with her friend Davy. When they find a barnacle-encrusted ring buried in the sand, they have fun imagining that it's lost treasure from a sunken ship and that they're in an adventure like 'Treasure Island.' But they soon realize they may be in over their heads--when other people seem desperate to get the ring!"--Back cover.