Frank and Joe Hardy are determined to bring to justice the vicious criminals who kidnapped their detective father while he was investigation sabotage of a road-building project in the Kentucky wilderness. After Mr. Hardy’s escape, the two young sleuths are spurred into action when he mumbles the word “Felix” and they discover a dossier of a notorious ex-convict was stolen from his files. The trail leads them to New York City but ends abruptly in a cemetery! With the new clue of a spiral symbol the boys head to Kentucky as part of a highway construction crew to track down the kidnappers and saboteurs.

Frank and Joe Hardy suspect that their best friend Chet Morton is the victim of a summer school swindle and offer to help get his money back. While probing a baffling burglary at the Seneca Indian Reservation in New York State they investigate Zoar College located nearby. A startling connection between the Zoar College swindle and the theft of the Seneca’s gold tribal relic Spoon Mouth propels the teenage sleuths into a series of perplexing and dangerous situations.

Mr. Drew is on the trail of an international ring of jewel thieves and asks Nancy to assist him. The trail leads to a summer resort area. Before Nancy has a chance to start work on her father’s case, a golf caddy tells her a frightening tale--in the dense woods nearby is an old wooden footbridge guarded by a ghost! Intrigued by the caddy’s story, Nancy decides to investigate. Several riddles confront the young detective as she attempts to solve the mystery of the haunted bridge and track down a woman suspected of being a key member of the gang of jewel thieves.

When the Hardy Boys take a winter vacation in Jamaica, Joe finds an ancient bronze death mask washed up near their beach house during a violent storm. Helping the Hardys and their friends in this bizarre mystery is William, a Jamaican boy, who flies to New York with startling news, only to be intercepted and held for ransom—the death mask! Frank and Joe must rescue William, plunge into their father’s airline-ticket theft case, and fly into a maze of danger in Africa.

The strange disappearance of a young Turkish client of Mr. Drew’s and the gift of an Oriental rug with a coded message woven into its decorative border start Nancy on a difficult search for a missing mannequin. What happened to the attractive figure that Farouk Tahmasp used in the display window of this rug shop? Who is trying to keep Nancy from finding it – and why? Tracking down the intricate trail of clues takes Nancy and her friends Bess and George, Ned, Burt, and Dave to Turkey. Their sleuthing leads them to the Grand Bazaar in the exotic city of Istanbul, where Bess mysteriously disappears. Suspense mounts when Nancy encounters a vengeful enemy at an ancient underground reservoir. Events move swiftly as Nancy and her friends try to solve this challenging mystery!

When Nancy receives a letter informing her she’s heir to a fortune, she decides to track down the sender, as well as the other Nancy Drew.

By mistake Nancy Drew receives a letter from England intended for an heiress, also named Nancy Drew. When Nancy undertakes a search for the missing young woman, it becomes obvious that a ruthless, dangerous man is determined to prevent her from finding the heiress or himself. Clues that Nancy unearths lead her to believe that the villainous Edgar Nixon plans to marry the heiress and then steal her inheritance.

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.