Verity Crisp's cousin has come to Peppercorn Valley. Her name is Ophelia Crisp, she is nearly ten and she has messy hair. She is also sullen, secretive and shrouded in mystery.
Before long Tan has reasons to suspect that Ophelia is a thief. But a Secret Spy should never jump to conclusions, so Tan sets out to build Ophelia's profile – and discover once and for all if she is a criminal. Tan's investigations lead her deeper into the secret life of Ophelia Crisp and, when Ophelia disappears, it is up to Tan to piece the clues together and find her before it is too late.