Looking forward to a visit at Sea Gull Beach, the Happy Hollister children have a wonderful time giving a play about pirates and American sailors. Then when they discover that a present they received from Uncle Russ, a lighthouse lamp, contains a real emerald, they are more eager than ever to get to Sea Gull Beach and find out where it came from. They have many exciting and new adventures during their search for the one hundred-year-old treasure which is buried with the MYSTERY ship. Pete, in an underwater outfit, visits the sea bottom, while Uncle Russ sketches cartoons of him from a glass-bottom boat. Pete