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 enters his sea gull kite in the big Kite Contest. Holly and Sue are caught on a sandbar with an incoming tide and are rescued by their new friend, Rachel. In their search for the treasure an old tomb and a strange half-house are among the unusual clues that lead the Hollisters to the treasure. To the Happy Hollisters, every day brings new fun and adventures as they eagerly welcome new experiences and new friends. That is why the stories about this lovable family make exciting reading.