Helena Willis is the author of popular mystery stories, including "El misterio del circo" and "El misterio del hotel." She also wrote "Święta w Valleby," a
Martin Widmark is a Swedish author celebrated for his children's mystery series. His works include "The Diamond Mystery" and "Nelly Rapp i Upiorna Akademia," which transport young readers into worlds of puzzles and adventure. Widmark's stories are popular for their engaging plots and accessible style.