Doug and his sister Barbara are puzzled nightly by sounds of digging on Seneca Hill, located in a rural section of Eastern United States. Out of curiosity, the children begin digging and discover some very strange objects: an arrowhead, a bayonet and Indian pottery. If Seneca Hill proved to be an important historical site, the Burnham Motel, operated solely by Doug's mother, would thrive with tourists. Mr. Jepson, a competitor, has the same idea, and later with the help of archaeologist Uncle Stan, facts as well as artifacts are unearthed leading to the eventual recovery of stolen objects which Mr. Jepson had in his possession. Troublesome Orson Tweedy and his mean brother turn out to be the diggers Old Jepson had hired. The story ends with a ""No Vacancy"" sign on Burnham Motel. Character reactions are unreal. A little chat with Mrs. Burnham, and Willard Tweedy ponders his mistakes and bad character. The plot is thin, lacking in tension or sufficient intrigue necessary in a successful mystery, nor do the illustrations help bring it to life.