Gwen and Jill are ready for the ultimate summer vacation at the beach. Their main goal? Winning the weekly sandcastle contest! They have the perfect design and are ready to build a sandy masterpiece. But every time they get close to finishing, something goes mysteriously wrong, ruining their hard work. Is it just bad luck, or is someone intentionally sabotaging their sandcastles? The girls will have to put their detective skills to the test to catch the culprit before the contest ends. Grab your sunscreen and join Gwen and Jill as they dig up the truth in this sunny, beachside mystery.