When Nancy arrives at the McGuire's fitness ranch in Arizona, she discovers that the future of the ranch is being threatened by unexplained accidents. Teaming up with a ghost, Nancy begins her search for a precious collection of ancient Kachina dolls and hunts for her elusive adversary, who is determined to prevent the ranch from operating.

When Nancy arrives at the McGuire’s fitness ranch in Arizona, she discovers that the future of the ranch is being threatened by unexplained accidents. Teaming up with a ghost, Nancy begins her search for a precious collection of ancient Kachina dolls that may unlock the motives of her elusive adversary. Will the person determined to prevent the ranch from operating succeed?

When she is told that a large inheritance from a Greek tycoon, meant for her friend Helen Nicholas, was stolen, Nancy agrees to find the culprit. A poisonous snake in a basket of apples and a strange symbol stamped on a rare Byzantine mask are clues in this mystery set in the beautiful and exotic country of Greece. These clues lead Nancy and her friends to a ring of art smugglers and to the secret of the Greek symbol.

In a response to a friend’s call for help, Nancy’s father, a lawyer, asks her to travel to mysterious Crocodile Island with her friends Bes and George to study the reptiles and try to uncover a group of suspected poachers. Upon their arrival in Florida, the girls are kidnapped but cleverly escape to pursue their detective work. Dangers mount as they cope with reptiles, enemy boats, and exciting chases after the men who are responsible for a sinister racket that involves many unsuspecting victims. In the end, Nancy makes a bold move to untangle the mass of clues, but she and Ned become imprisoned in the enemy’s submarine and are held for ransom!

When Nancy and her friends ride deep into the Sawniegunk Forest in search of a flying saucer, they find themselves in the middle of more than one mystery. Wildcats, runaway horses, deadly snakes, and a disappearing Indian keep the sleuths tangled in danger and suspense.

When Nancy Drew receives a valuable moonstone as a gift from an unknown person, she is amazed and puzzled. But it is only the first of several startling events in this complex mystery that challenge the ingenuity of the pretty sleuth. Why are the Bowens – a missionary couple who recently returned to the United States – having so much trouble finding their missing seventeen-year-old granddaughter, Joanie Horton? Nancy and her friends travel to Deep River, the town where the young Jonie lived. From the motel where Nancy and her friends stay, they can see an intriguing castlelike structure with a drawbridge. Gossipy Mrs. Hemstead at the village tearoom insists that Moonstone Castle is haunted. Curious, the three girls attempt to explore the abandoned castle, but an ominous voice warns them away. Other strange happenings in Deep River convince Nancy that there is a connection between Moonstone Castle and the mysterious moonstone gift. But what is the significance? And where does the baffling disappearance of Joanie Horton fit into the intricate puzzle?

Nancy Drew must search for a flight of 99 steps to solve the mystery of a friend’s weird dream. Her search leads her to France, but before she leaves the United States, an unknown person calling himself Monsieur Neuf warns the young sleuth not to pursue her mission. With her friends Bess and George, Nancy arrives in Paris to join her father who is working on another case: to find out what, or who, is frightening wealth financier Monsieur Leblanc into selling large amounts of securities. Startling discoveries convince the young detective that Mr. Drew’s case and her own mystery are linked by the 99 steps, and that a mysterious man has a strong hold over Leblanc. Is it blackmail? Nancy’s quest for further clues leads to the romantic chateau country in the Loire Valley, where a web of danger closes in tightly around the three girls.

A magazine article offering a large reward to anyone who can find a missing medieval stained-glass window intrigues Nancy. She asks Bess and George to join her on a search in Charlottesville, Virginia. Before the three friends leave River Heights, their adversary tries to get them to postpone the trip. But no luck. Nancy is determined to carry through her plans. During the girls' investigation of old southern mansions, they encounter a ghost who turns the tables and makes them disappear. Eerie sounds come from a beautiful estate that is surrounded by a high brick wall. Why will the owner allow no one to enter?

Nancy and her friend Helen visit their friend Emily Willouby at the Lilac Inn, which Emily now owns, to help her plan her wedding. Emily plans on selling inherited diamonds in order to help fix up the Lilac Inn. However, Nancy soon learns that someone has been impersonating her and making expensive purchases under her name. Soon after, Emily's diamonds are stolen! Can Nancy find the thieves and recover the missing diamonds?

Thrilling, dangerous adventures confront Nancy Drew while on a safari in East Africa with a group of American college students. Excitement runs high as the teen-age detective delves into the theft of a fabulous sapphire formed by nature millions of years ago. The mystery starts in Nancy’s home town. Her lawyer father’s client, Floyd Ramsay, who fashions beautiful and unusual synthetic gems, is accused of stealing the magnificent spider sapphire and exhibiting it as his own creation. Mr. Ramsay’s enemies blackmail him and by their vicious acts try to deter Nancy from going on the safari. Readers will join Nancy as she uncovers a nefarious scheme and solves the strange disappearance of an injured jungle guide.