When eccentric Thaddeus McClintock invites Frank and Joe Hardy to accompany him on a sea voyage, the teenage investigators become entangled in a web of mystery. Who is trying to block the three from securing reservation on freighter ships that carry passengers? The determined efforts of Frank and Joe lead to a hazardous game of wits with a ring of slippery smugglers and to a dramatic confrontation on the high seas. Here is an exciting, action-filled mystery that will keep the reader on edge with suspense.

The Hardy brothers embark on a freighter trip under mysterious circumstances and find themselves involved with a smuggling ring.

When eccentric Thaddeus McClintock invites Frank and Joe Hardy to accompany him on a sea voyage, the teenage investigators become entangled in a web of mystery. Who is trying to block the three from securing reservation on freighter ships that carry passengers? The determined efforts of Frank and Joe lead to a hazardous game of wits with a ring of slippery smugglers and to a dramatic confrontation on the high seas. Here is an exciting, action-filled mystery that will keep the reader on edge with suspense.

A dying criminal confesses that his loot has been stored "in the tower." Both towers of the looted mansion are searched in vain. It remains for the Hardy boys to make an astonishing discovery that clears up the mystery and clears the name of a friend’s father.

Together in this one book are two of the Hardy Boys’ oldest mysteries that began the classic mystery series of the sleuthing siblings. In The Tower Treasure, the Hardy boys' summer is ruined by a red-haired robber striking all over town. No robbery is more devastating than of Tower Mansion, home to one of the wealthiest families around. To prove the mansion’s caretaker is innocent, the Hardy boys will have to solve the mystery of the stolen jewels before time runs out. In The House on the Cliff, Frank and Joe are asked to help out their famous private detective father on his latest drug smuggling case, which sends them to an old house on a cliff to serve as lookouts. But when cries for help lure the boys inside the house, they realize they could be in more danger than they thought.

Valuable electronic parts containing platinum are being stolen from shipments made by Stanwide Mining Equipment’s cargo planes, and Frank and Joe are called upon to assist their world-renowned detective father solve the baffling case. While posing as Stanwide employees, the boys look into the truth behind the chief pilot’s death at sea. The puzzling trail of clues leads the young sleuths to an uninhabited Caribbean island, but the final, and most startling, discovery is made in the boys’ home town of Bayport.

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.

The boys once again have jumped into the thick of a complicated mystery. Samuel Blacksone and his brother Ruel Rand live on adjacent properties, and it appears that one of them is out to hurt the other because they are both attacked. Frank and Joe soon learn that treasure is rumored to be hidden between the two properties, and as they investigate, they learn that others are involved in the apparent plot between the two brothers. Spooky mansions, secret passages and rooms, mysterious characters, and a monster provide an enjoyable atmosphere to this Hardy Boys mystery.

A million dollars’ worth of gold bullion has been stolen from the Wakefield Mint under strange circumstances. Mr. hardy is asked to investigate but before long his life is threatened, and he asks Frank and Joe to help him. The boys fly to Zurich, Switzerland, hoping to get information at the Swiss Gold Syndicate and to find the man who has stolen a valuable ancient gold figurine from a New York museum. Their search on both counts seems futile as they return to the United States where they uncover clues that lead them to an adventure in the Yucatán jungle. But the Hardy’s travels lead to nothing but new doubts and nagging suspicions. And now their lives are in danger.