Despite warnings from a stranger, Nancy sets out for France to search for a flight of 99 steps which may help solve the mystery of a weird dream and a possible case of blackmail.
When strange accidents start occurring at the local pioneer village, Nancy, Bess, and George go undercover to determine if the village is really haunted by the Lantern Lady, or if the accidents have a more deadly cause.
While helping the police find the owner of a mysterious house with a crooked staircase and an unpredictable robot, Nancy Drew, girl detective, also helps capture a swindler.
Nancy is warned not to go to South America with a group of girls as she had planned. However, she proceeds and investigates a mystery on board which leads her to a cache of stolen jewels.
