Her house is full of ghosts, there's a wild beast in the garden and her best friend lives in a cave! All Olivia Kidney ever wanted was a nice, normal life. But that's just not possible for a girl who can talk to spirits.

Olivia's mad world gets even madder when she begins to investigate a mysterious anthropologist who lives in an underground maze beneath the streets of New York. There she meets a gang of ghost kids who have been trapped for over a hundred years. Helping them out is one of her wildest challenges yet!