Frank and Joe hardy suspect that their best friend Chet Morton is the victim of a summer school swindle and offer to help get his money back. While probing a baffling burglary at the Seneca Indian Reservation in New York State they investigate Zoar College located nearby.

Clues that Frank and Joe uncover indicate that there is a connection between the Zoar college swindle and the theft of the Seneca's gold tribal relic Spoon Mouth. This startling discover propels the teen-age sleuths into a series of perplexing and dangerous situations.

Two strange-acting college professors, a valuable coin collection, and a taciturn Indian who refuses to discuss the mystery surrounding Spoon Mouth-all blend into a fast-paced story with several surprise twists that will thrill the vast legion of Hardy Boys fans.