Seth and Julia Ambrose are pros at solving mysteries at their favorite amusement park. But can Julia solve her biggest mystery yet without her big brother? After finding a ruby at Waldameer, Julia and her friends are soon searching the concession stands for stolen jewels worth millions. Time is ticking because the thieves who stole the jewels are coming to claim their lost loot. Can the kid detectives outwit the thieves? Does Julia have what it takes to lead the team by herself? Find out in this exciting all-girls mystery about believing in yourself!