Mercedes Bent is 15. Her dad, Big Al, ran several rackets in the East End until his premature death a few years back. Now his scams have been taken over by Mercedes' twin brothers, Chubby and Frankie. Mercedes is stuck in her smart school, The Daphne Pincher Academy for Young Ladies, because Big Al wanted her to be brought up 'a proper lady'. There she runs the book on everything - from whether it will rain tomorrow, to the likely resignation of various teachers. Mercedes is horrified to discover that her upcoming work experience placement is in a bank - not at all what she had in mind! Then, arriving at the bank, Mercedes falls for Zak. Suddenly life doesn't seem so bad. But then Mercedes discovers that her brothers are hatching a plot to rob the very bank at which she'll be working - and it's going to look as if she's set Zak up! She'll have to find a way to stop her brothers in their tracks, before it's too late ...