Great Aunt Maud visits seasides the world over and has become quite the pebble collector. Pebbles of all shapes, sizes and colours and even one that looked a bit like Elvis Presley if you held it up to the light and squinted a bit. Her favourite pebbles, however, are Flora, Flick and Finn. One by one, and by strange and unusual ways, each child arrives at the stage door of Great Aunt Maud's theatre in the heart of London. Now that the Pebbles are a little older, they spend their summer holidays backstage with an extraordinary cast of theatre acts - Dante the miraculous magician, Petunia the storyteller and seventy-year-old contortionists - the Fortune Sisters! One day, as they are exploring the many nooks and crannies of the theatre, they discover something they were never meant to find . . .