Mr Flatley receives a letter from his Great Aunt Jemima informing him that she has left part of her fortune to him in her will. Mr Flatley is going to be a millionaire! The news soon spreads throughout the school and the kids and Mrs King are all clambering over Mr Flatley in the vain hope some of his fortune will be passed to them. However, there's a small problem - Mr Flatley also receives a ransom letter threatening to blow up the school unless he turns the money down. Frank promises him that he'll sort it out, and the team are on the case. Assuming the blackmailer must have been left out of Aunt Jemima's will, it must be one of the other Flatleys, so as Mr Flatley's other relatives arrive at St Hope's for the reading of the will, the spies investigate further. There's Jeanette Flatley, a posh vicar who insists on speaking in nonsensical street slang; Nozzy Flatley, a failed rock musician from Birmingham; and Hamish Flatley, a Scottish University lecturer in advanced chemistry. All have motivation for wanting the money, and the evidence points to all three - can the young spies discover who is responsible before the school is blown sky high?