Martha & The Medium Sized Man' is the latest adventure in the 'Martha' series.
This time Martha learns all about the Second World War when she puts on the Magic Ring and goes back in time to Germany in 1942.
Who is The Medium Sized Man?
Why has the horrible Herr Hitler locked him up in the escape proof Castle Colditz?
And how does Martha use a tortoiseshell penknife to help him escape from the nasty Nazis?
All these questions and more are answered in this exciting new adventure.
All proceeds from sales of this book will go to The Great Ormond Street Hospital for Children.