The fourth globe-trotting installment in the exciting Secret Agents Jack and Max Stalwart series, by beloved children's author Elizabeth Singer Hunt (author of the award-winning Secret Agent Jack Stalwart series).

Now Jack teams up with his older brother Max to solve a thrilling California puzzle, using their special training as Global Protection Force agents.

In the foothills of California's Sierra Nevada Mountains, an unbelievable discovery is made: $10 million in rare coins dating back to the California Gold Rush Secret Agents Jack and Max Stalwart are sent to protect the treasure.

But almost as soon as they arrive, it vanishes into thin air. Little do they know that the culprit is someone from Jack's past. Unfortunately for the brothers, the criminal isn't only after the loot. He wants revenge.