In the 11th title in this mystery series, Meg Mackintosh receives a puzzling letter on her birthday, which happens to be on April Fools' Day. She sets off following a trail of puzzles and clues which lead her to a curious old house...and the sender of the letter? Is this a real birthday present or an April Fools' Day prank? Meg uses her sharp detective skills to solve the case. Clues can be found in the illustrations and questions are posed to the reader to help them solve the case along with Meg.