A black-robed figure and a marble tiger are the clues in the exciting mystery surrounding a private museum

When Professor Crandall receives a warning note to abandon a valuable fountain he has recently purchased, the Dana sisters decide to help him

Two girls' search for a silver dolphin mentioned in a will is hindered by a hostile fortune-teller and an elusive thief.

The Dana sisters spend their spring vacation solving a mystery involving a phony automobile raffle, a wax bust of Queen Victoria, a stolen diamond, and a sculptress.

The Dana girls embark on an exciting voyage to Portugal, where they have been invited to help solve a mystery

Jean and Louise Dana attempt to solve the cases of sabotage and theft at a resort town's restoration project

While vacationing in Europe, the Dana sisters agree to help a former Austrian prince locate his family's long lost heirlooms, a search that takes them into the dangerous snow-covered Swiss Alps.

The Dana girls and their friends try to locate a missing sea captain last seen on Chincoteague Island off the Virginia Coast.

Attempting to recover a sacred gold statue stolen from a friend, the Dana sisters track the thief to Thailand where they encounter a series of harrowing experiences.

Louise and Jean Dana fly home from Thailand completely unaware of the exciting adventures waiting for them just a few hours away. But even before their plane lands in San Francisco, Louise's precious star sapphire ring is stolen, and the girls are plunged into a new mystery. Before the Danas have a chance to investigate it, a fellow traveler, Janet Crane, begs them to find her grandfather who has disappeared somewhere in the rugged terrain of the Sierra Nevada mountain range in eastern California. The two mysteries must wait, for the girls have promised to visit their aunt, Mrs. Carol Reed, in Sacramento. Aunt Carol tells Louise and Jean a family secret about a chest of gold nuggets which was buried for an ancestor during the historic gold rush of 1849 by his devoted Chinese servant—and now the girls have three thrilling mysteries to satisfy their love of adventure. Four generations of Reeds have searched for clues to the treasure with only a half-charred letter to guide them. Now Jean and Louise, with their sharp instinct for solving the most complicated riddles, decide to add their three mysteries together—and come up with a triple solution.