With only the slender clue of an arrow-shaped tie clasp, Frank and Joe Hardy pick up the trail of a cunning gang of thieves responsible for a wave of jewelry-store holdups. But their investigations are interrupted when a desperate plea for help comes from their widowed cousin who lives on a cattle ranch in New Mexico. Frank, Joe, and their pal Chet fly there immediately, and manage to put an end to the trouble at the ranch and solve the jewelry-store robberies.

The Hardy brothers interrupt their investigations of jewelry-store holdups to answer a plea from their cousin on a New Mexico cattle ranch.

A series of museum thefts launch the Hardy Boys on this baffling mystery. Rare collections of ancient pirate treasure are being stolen, so Frank and Joe are asked to stake out the Black Parrot, a suspicious freighter docked in Bayport Harbor. This whirlwind chase after a self-styled pirate king in the Caribbean stronghold of the Empire of the Twisted Claw makes a gripping tale of suspense and high adventure.

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.

Another exciting mystery begins for Frank and Joe when they help a stranger who has had an accident with his car. The man introduces himself as John Mead, owner of a nearby estate. But when the Hardy boys find an odd-looking house key and try to return it, they realize that John Mead died five years ago! They are even more amazed when they find that the intricately carved doors in the deserted mansion have no visible knobs or keylocks. What happens when Frank and Joe discover that there is a link between their father’s case of thieves and the mysterious Mead mansion will keep the reader on edge with thrills and suspense.

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.