The Mystery at the Moss-covered Mansion (Nancy Drew Mystery Stories, #18)

Nancy's father Carson Drew enlists her help in tracking down a missing heiress, and Nancy, Bess and George stumble upon a mysterious moss-covered mansion. The girls learn someone was murdered near the mansion and they hear strange noises coming from inside the building. Action bounds in this thrilling adventure involving gypsies, a missing heiress, a needy elderly lady, a reclusive artist, an airplane accident, and a forest fire