The Sigma Force must solve a centuries-old secret involving coded prophecies about dark events leading to a future apocalypse.

"Jacobite exile Mary Dundas is filled with longing--for freedom, for adventure, for the family she lost. When fate opens the door, Mary dares to set her foot on a path far more surprising and dangerous than she ever could have dreamed. As Mary's gripping tale of rebellion and betrayal is revealed to [amateur codebreaker Sara Thomas, she] faces events in her own life that require letting go of everything she thought she knew--about herself, about loyalty,...

Cryptographer Susan Fletcher finds herself fighting for her country, her life, and the life of the man she loves when she is called in by the National Security Agency to decipher a mysterious code and discovers a plot that has the power to cripple U.S. intelligence.

After a mountainside massacre yields a grim message, Painter Crowe, director of Sigma Force, must join with Commander Grayson Pierce and an unlikely ally if he is going to get to the root of a conspiracy that stretches back to a lost prehistoric colony in America.

Amy and Dan Cahill have been located once again, this time in the company of the notoriously unreliable Alistair. Spies report that Amy and Dan seem to be tracking the life of one of the most powerful fighters the world has ever known. If this fearsome warrior was a Cahill, his secrets are sure to be well-guarded.

Amy and Dan have been found unharmed! But perhaps not for long--the ruthless Irina Spasky is right on their tail. Book 5 takes Dan and Amy on their most dangerous quest yet, one that brings them face to face with the only force capable of scaring the vicious Lucians: the Madrigals. Dan and Amy are on their most dangerous quest yet, one that brings them face to face with the only force capable of scaring the vicious Lucians: the Madrigals.

What would happen if you discovered that your family was one of the most powerful in human history? What if you were told that the source of the family's power was hidden around the world in the form of 39 clues? And, what if you were given a choice of taking a million dollars and walking away or getting the first clue to the mystery? If you're Amy and Dan Cahill, you take the clue, and begin a very dangerous race!

Throughout the hunt for the 39 Clues, Amy and Dan Cahill have uncovered history's greatest mysteries and their family's deadliest secrets. But are they ready to face the truth about the Cahills and the key to their unmatched power? After a whirlwind race that's taken them across five continents, Amy and Dan face the most the difficult challenge yet -- a task no Cahill dared to imagine. When faced with a choice that could change the future of the world,...

Kirby "Zig" Zigonski lives for the world of simple circuits, light bulbs, buzzers, and motors. Electronics are, after all, much more predictable than most people--especially his father, who he hasn't seen in over a year. When his dad's latest visit is canceled with no explanation and his mom seems to be hiding something, Zig turns to his best friend Gianna and a new gizmo--a garage sale GPS unit--for help. Convinced that his dad is leaving clues around...

Thirteen-year-old Ruby, a genius code-cracker and daring detective, gets an anonymous call setting a challenge that leads her to the headquarters of Spectrum, a highly secret anti-crime agency that needs her help to crack a code, but soon Ruby uncovers dastardly plans of the Fool's Gold Gang.