When Amy and Dan Cahill trace the footsteps of a formidable military leader from the Cahill bloodline, they uncover a devastating secret about the family that changes everything.

Journeying to the ancient city of Babylon when Bhegad tracks down Marco, the companions face a daunting choice involving a dire trap and a long-lost figure from Jack's past.

After Marco's betrayal, Jack McKinley and his friends must face their own demons and engage in a battle with foes long gone.

Jack and his friends desperately search for the rest of the lost Loculi and confront the armies of Artemis in order to rescue Aly, who has been pulled back into Atlantis by King Uhla'ar.

Ever since Corey Fletcher found out that he's the world's first "throwback," with the power to not only visit history, but change it, he's been spending as much time in the past as possible. Corey loves using his skills to fix problems and help his friends and family. But as Corey becomes more and more addicted to rewriting history, he learns that time travel might change him in ways he may never be able to reverse. Aware now that he can't keep going...

Fourteen-year-old Amy Cahill and her younger brother, Dan, thought they could return to their regular lives when they found the 39 Clues that safeguard their family's great power. But they were wrong. Powerful enemies -- the Vespers -- have been waiting in the shadows. And they'll stop at nothing to grab the Clues. Four powerhouse authors unite to expose the 500-year old secret struggle between the Cahills and the Vespers. The Vespers are rising ......

Sibling spies Amy and Dan Cahill team up with the unpredictable Alistair Oh to uncover the secrets of a legendary warrior, secrets so well-guarded, they could prove deadly to anyone who seeks them.