 The main characters in the story are two young Americans, Aidan and Sarah Cooper.One summer morning Aidan and Sarah, who are visiting their grandfather, discover a secret compartment in his battered wooden desk.Inside is a yellowed envelope that contains a piece of very thin, almost translucent, white paper, on which, handwritten in black ink, are a series of seemingly random lines; among them are what appear to be fragments of letters, but not enough to make sense.