Nancy, Bess, and George want tickets to see pop singer Katy Sloan play at the River Heights Amusement Park--but their parents say they've already filled their summer theme-park quota. So the girls decide to turn lemons into lemonade by earning their own tickets--with a lemonade stand!

Unfortunately Lily Ramos, a new girl in River Heights, has the same idea. She's the niece of the owner of the town's newest and hottest café, and her stand is equipped with café tables, gourmet treats, and a rolling library cart! Good thing Nancy has a secret weapon: Hannah's family lemonade recipe!

The girls are all set to whip up the lemonade--until the recipe is replaced by a blank sheet of paper! Nancy, Bess, and George set out to find the thief! Could it be Lily, whose stand may be fancy but whose lemonade is totally yucky? Or a sneaky contestant on Ready, Set, Cook!, the hot new kids' cooking contest show? It's up to the Clue Crew--and you--to find out!