Catherine/Natalie Unknown

Catherine/ Natalie Unknown is a girl who gives clues to Aunt Kathren and Evan. When they find a thing written on the letter, Catherine slowly turns into Natalie Unknown.

Books that Catherine/Natalie are in

 * The Roller Coaster Jet, Silver Bullet, Boomerang, and Kingda Ka
 * So Many Questions
 * Block Town
 * Our Last Journey...Goodbye