Matilda, an 11 year old girl who wants to be a great detective, has a mystery on her hands when she tries to buy a microscope from a man. What I loved about this book as a kid was the gender role switches Anderson writes. This book was published in the early seventies and it was refreshing to have a strong willed 11 year old adventurous girl detective. Her younger brother's dream was to become a world class chef. (I know as ADULTS, most chefs are men, but there was something nontraditional about a little boy crying over his souffle). Good book.