Riz Chester is an average 11-year-old girl. She can't do anything special and is average at school. But Riz is particularly picky, she notices when the teacher is 2 minutes late, or when the food brand used in the cheese sandwiches changes. She also notices when money doesn't feel quite right.

Spotted by a police officer, Riz gets called in for questioning. She demonstrates she indeed does easily notice the difference between the normal notes and the counterfeit ones, even though before her interaction with the officer she had never heard of counterfeiting. The officer explains that there is a ring of counterfeiting occurring locally but they haven't been able to pinpoint the criminal source. Mum cannot remember where the notes came from, but something sticks out to Riz when she thinks about it later. She recruits her friends to help her help investigate, carefully planning a course of action to track down the counterfeit notes. With the help of Riz and her friends, the police uncover the counterfeit operation