Now you see them, now you don't... What would you do if you could become invisible? Creep around, unseen? Listen in to other people's conversations? Twins Carrie and Conrad, and their friends Peter and Charlotte do all these things, and much more, when a new girl at school - Rosie - shows them her secret: how to make yourself invisible.

It's exciting, and it's fun. It can also be frightening... and dangerous. Especially when Rosie's dad becomes a suspect in a local crime and the gang go invisible to find the real crooks...