Mandie and the New York Secret

After a visit to Mandie's Cherokee kinpeople, Mandie, Celia, and Joe prepare for their trip to New York to visit Jonathan Guyer. Just before they leave, though, Mandie receives an urgent wire from Jonathan: "Hurry on to NY. I have just discovered a great big secret from long ago." Mandie is wild with curiosity. But when they finally get to New York, Jonathan has gone to Long Island and won't be back till the next day! Can Mandie wait another day to learn the secret? What on earth could it be?