In this third book in the Charlie Thorne series from bestselling author Stuart Gibbs, Charlie tracks down Cleopatra's greatest treasure in Egypt. Charlie Thorne is a genius. Charlie Thorne is a renegade. Charlie Thorne isn't going down without a fight. After tracking down incredible discoveries by Einstein and Darwin, Charlie is back. This time, the great ruler Cleopatra has left behind an extremely valuable and powerful treasure, its location encoded on an ancient stone tablet. In 30 BCE, Cleopatra and her husband, Marc Antony, lost their war against Octavian for control of the Egyptian Empire. However, Cleopatra knew Octavian was really after the mysterious item that was the source of all her wealth and influence, so she hid it before committing suicide. She left a series of devious clues behind for her children to find it, but they were lost to history ... until now. In a breathless adventure that takes her across the globe, Charlie must fight for her life against ruthless enemies, match wits with Cleopatra, and solve the two-thousand-year-old mystery to prevent the most powerful treasure of the ancient world from falling into the wrong hands.