Jeannie and Robert arrive at Lost Creek. Robert believes he has seen bigfoot. One of the national land marks there is a mountain that looks like an apes head called Stone Face.

The kids hear the tale of a local legend about a buried treasure on Stone Face. Jeannie gets invited to the local town dance.The kids decide to investigate the treasure.

They do research in the archives of the newspaper ( run by Jeannies grandfather). The treasure is supposedly buried on Stone Face so the kids decide to hike up there. They then get scared off.

Jeannie and Robert continue to investigate. They interview the oldest residents in town , trying to see what they remember about the legend.The town is preparing for founders day, and as they set up the parade, a stranger approaches Jeannie and threatens her, he wants her to stop snooping.

As their investiagtion leads back to the mountain, the kids are once again scared off - this time by Bigfoot? As they run down the mountain they perchance to see a light from way atop Stone Face, in fact it's in the eye of the monkeys skull. When thye climb to the top they discover it's a cave. They find a secret meeting of a few town members going on.They hover outside listening. When they break in on the group - everyone scatters, but one of the towns people sets off some dynamite which blows up the cave. After much explaining the kids finally discover what the treasure is, and why the legend was born.