In "The Secret of the Sundial," Penny Parker is a young amateur sleuth who becomes entangled in a mystery involving a mysterious sundial. The story unfolds as Penny discovers the sundial and starts investigating its secrets. This leads her into a series of adventures where she encounters clues, puzzles, and possibly even danger. Throughout the book, Penny uses her intelligence, bravery, and determination to uncover the truth behind the sundial and the mystery surrounding it.