When Kate Farris and her friends witness a cantankerous, old man drop part of a hand-drawn map, they try to return it to him, but the cranky man drives off. Upon investigating, they learn the man is Mr. Benson, an old prospector and hermit who lives in the nearby hills. After several horseback rides along the trails to search for the man, the kids find more adventure than they anticipated. When Kate and Tori overhear two men discussing Mr. Benson, rumors of the gold he's found, and how they plan to rob him, Kate and her friends know they have to warn Mr. Benson before the thieves can strike. But what will happen if their plan backfires, and the men come after them?