The Sierra Gold Mystery — Carolyn Keene

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.