Thirteen year-old Ailish, a feisty Irish fortune-teller, is about to become part of history. She becomes trapped on the mightly Great Eastern just as the ship sets off on its voyage to lay the very first trans-Atlantic telegraph cable. Escape is impossible! Ailish must pretend to be a boy to keep from being pitched into the ocean by the superstitious sailors, while dodging a dangerour ruffian who has stolen her golden treasure. She frequently gets help from a pale young boy named Davy, who seems to know everything about the Great Eastern, but won't ever appear up on deck.