Mikey and Sandy were about to celebrate their eighth birthday, but what they thought was going to be an ordinary birthday turns out to be not so ordinary after all. In fact, it is a most extraordinary birthday full of magical, incredible surprises and amazing adventures that the twins could never have expected. It all starts when they begin to build a gigantic sandcastle at the beach. As they dig deeper into the sand, they hear a tiny, mysterious voice crying for their help. Who is begging to be saved? What do they need to be saved from, and should the twins risk their own lives to save them? They decide to take that risk, and this is when all the magic begins.