Fatty, Larry, Daisy, Pip, Bets and Buster become involved in a very peculiar situation when a series of unsigned letters are sent to various people in Peterswood.

The Five Find-Outers — Fatty,[1] Larry, Daisy, Pip and Bets, and their Scottie dog, Buster — are shocked when someone starts sending anonymous spiteful letters to several people in their village of Peterswood.

Pip and Bets are involved when their young maid Gladys receives one of the letters, which reveals a secret — her parents are in prison for theft and she has lived in a girls home.

They make a list of suspects — could the letter writer be Mr. Nosey a busybody or Miss Tittle a lover of gossip — or someone else?

Their arch-enemy, village policeman Mr Goon is also on the case, and the children must hurry to solve the mystery before he does.