Having overthrown Black Texta and his evil sidekick Rubber, Penny and her friends can get on with helping Ralph with his schoolwork.
But someone is writing graffiti on Ralph's school books, vandalising Sarah's entry in the school colouring competition and turning Ralph's coloured pencils against Gloop. With help from Sarah's pencil Polly, Penny goes undercover to find out who is committing these dastardly deeds. Together with Polly, Penny sneaks into the other children's pencil cases to find out who is responsible.
After close calls in the pencil cases of Lucy the Stealer, Sean the Chewer and the strange Floating Healers, Penny and Polly stumble across the lair of the evil culprit, and discover that it will take all their ingenuity to save not only themselves, but all the children in Ralph's class from the evil plot.
