While trying to determine who stole their music box, the Twiddle twins find unusual clues such as banana peels, a coconut shell, and a chocolate bar wrapper.

After moving into their new house, the twins and their parents are awakened in the middle of the night by a strange tapping noise and are convinced that they have a ghost.

When Tabitha Twiddle carelessly leaves her beloved toy hippo Blippo in a playground sandbox, she and her twin brother must retrace her steps to find him.

Tabitha and Timothy Twiddle, twin hippos, must prove to their neighbor that they are not responsible for the mysterious footprint left in the wet cement in front of his house.