"Legend says that an eccentric millionaire hid a treasure somewhere inside the legendary 'White City' of Chicago's 1893 World's Fair. Elsa Rutledge believes that treasure may hold the key to finding her long-lost grandfather. Relying on the World's Worst Time Machine once again, Elsa and Liam are on the hunt! They're not the only ones. To stay one step ahead of all the other time travelers, the kids must upgrade their technology, forge new friendships, and unearth long-buried secrets. Also, they're going to need a lot of pickles" -- Back cover.