The Boxcar Children discover an old wedding photograph and a riddle while on a visit at a neighbor's house, and they embark on a spy game designed by the house's original owner.

"Marie-Grace can't wait to begin her journey up the Mississippi River with her father. The steamboat they're traveling on is the biggest and fanciest boat Marie-Grace has ever seen. It's crowded with all sorts of interesting passengers, including Wilhelmina Newman, a girl her age. Wilhelmina is traveling alone, and she's carrying a secret in one of her trunks--clues to hidden Gold Rush treasure. Marie-Grace and Wilhelmina have to unravel the clues...

As a slave in the Kipchak Khanate, Jinghua has lost everything: her home, her family, her freedom. She becomes an unlikely conspirator in the escape of Prince Khalaf and his father from their enemies across the vast Mongol Empire. Jinghua hatches a scheme to use the Kipchaks' exile to return home. Her feelings evolve into a hopeless love, as Khalaf seeks to restore his kingdom by forging a marriage alliance with Turandokht, the daughter of the Great...

The magic tree house has whisked Jack and Annie to ancient Egypt. Inside a pyramid, Jack and Annie find a long-dead queen who needs their help solving a centuries-old riddle. If only they can find their way through the pyramid's maze!