My naughty little sister is the naughtiest little girl in the world. There's double trouble when my naughty little sister gets together with her best friend, Bad Harry! There's a peculiar pile of moldy crusts on the floor--where has it come from? Bad Harry gets covered in polish and sawdust, but he doesn't think that's naughty at all. And why on earth are those children taking pieces of cheese and bacon-rind to the library?