Scholar Jules Addison and scavenger Amelia Radcliffe join forces to unravel secrets of a long-extinct civilization, only to discover something that could spell the end of the human race.
Battle-hardened World War II sergeant Joe Enders tries to maintain a professional distance when he is assigned to, protect Ben Yahzee, a young recruit fluent in the so-far unbreakable battlefield code based on the Navajo language--mindful of the unspoken order to kill Ben rather than let him be captured by the Japanese.
Amy and Dan, members of the powerful Cahill family, try to uncover the thirty-nine clues which will reveal the secrets of their lineage and find out what really happened to their parents.
Steve's lie about liking to break codes comes back to haunt him when Quinn gives him a message to decode, and he must either figure out the code or tell Quinn the truth.
During World War II, eleven-year-old Felicity is sent from London to Bottlebay, Maine, to live with her grandmother, aunt, uncle, and a reclusive boy who helps her decode mysterious letters that contain the truth about her missing parents.
Thirteen-year-old Ruby, a code-cracker and detective, gets an anonymous call that leads her to the headquarters of Spectrum, a highly secret anti-crime agency that needs her help to crack a code, but she uncovers an evil plan by the Fool's Gold Gang.
