The Invisible Island

While picnicking on Squaw Island, a group of friends find a $500 bill. But when they return the next day, the whole island has disappeared and they must figure out the mystery to this vanishing act.
I is for Island... One beautiful day, Dink, Josh, and Ruth Rose pack up a basket and wade out to Squaw Island for a picnic. Before they can even spread their blanket, they find a hundred-dollar bill in the sand! But when the kids come back the next day, the entire island has mysteriously disappeared. What is the secret of Squaw Island? Find out in this, the ninth book in this highly collectible series guaranteed to please all second- to fourth-grade sleuths.