In this illustrated children's book, a group of cousins on vacation uncover a message in a bottle that points them to buried treasure.It's summertime in Beach Haven Terrace, and seven cousins (Molly, Emma, Caroline, Grace, Maggie, Ellie, and Lucy-all named after the book's young co-authors) are staying with their grandmother before "the boys" arrive from summer camp. The eldest look after the younger girls and play on the sandy beaches. One day, they find a bottle in the sand, supposedly sent by crewmembers on a lost Spanish ship, which contains an English-language message of hidden treasure, and the girls collaborate to follow a list of clues to its source. The authors offer realistic sisterly dynamics (" 'Women! And you are my women!' Molly said, imitating the voice their Pop Pop") and have a documentary eye for the experience of adolescent vacationing. The girls take a tour of their summer town on buses and tandem bicycles, spurred by their own imaginative sense of adventure. The historical context of in this light, low-stakes mystery becomes increasingly implausible; one clue, for instance, is related via a musical performance on a family-fun pirate ship. Leslie's ink-and-watercolor images feature appealing composition and provide helpful accompaniment to the text with serene Atlantic overcast beaches, lighthouses, grasses, and sandy shoes. However, the images' small size makes the details hard to see. Overall, this collaborative project captures real affection and a feeling of leisure and adventure that will be comforting to emerging chapter-book readers. The mystery lacks polish, logic, and clear resolution ("And who was it, exactly, who had left the girls those clues? I leave it to you, dear reader?."). Still, the O'Meara, Schreier, and Hennessey team deliver a pleasant work.An often charming summer story, hampered by some puzzling story elements.