The 39 clues. Unstoppable

Amy and Dan Cahill have their final confrontation with twisted billionaire J. Rutherford Pierce, a man whose power has no limits and is one step away from being elected president.

Amy and Dan Cahill have their final confrontation with twisted billionaire J. Rutherford Pierce, a man whose power has no limits and is one step away from being elected president.

When her younger brother Dan's life hangs in the balance, Amy Cahill must make a terrifying decision between saving him by unleashing a dangerous evil into the world, or losing him forever. Includes six game cards and a link to additional online information about "The 39 Clues" series.

Thirteen-year-old Dan Cahill and his older sister, Amy, are the latest family guardians of a secret serum that can turn anyone into the most powerful person on earth. When one mistake leads to the serum's disappearance, it's Dan and Amy's job to get it back.

Dan Cahill, thirteen, and his sister Amy face their greatest threat yet--an enemy that has found a way to use the power of the Cahills against them. From hot deserts up to the Arctic Circle, Dan and Amy try to escape this enemy--until Dan faces the worst thing he could imagine: his own sister's betrayal.