Judy Bolton, Irene Lang, and the rest of their friends attend the presentation of a fortune teller at the Farringdon theater. Irene is called to the stage, and the fortune teller warns Irene not to go to New York to marry Dale Meredith. Irene becomes nervous and worried after her consultation with the fortune teller, and Judy fears that Irene will ruin her life based on the dire prediction. Judy knows that the fortune teller is tricking the audience in some fashion, but how can she prove that the fortune teller has some unscrupulous means of acquiring information? And how does the fortune teller determine which people to ask on stage for a consultation? Judy's wits are put to the test as she struggles to find a solution to this complex mystery in time to prevent superstitious Irene from making a drastic mistake.