"Nora and Ben's younger sister Birdy loves to keep secrets...One day Birdy watches her mother spit into a tube, ready to send it off to find out more about herself...Birdy spits into a tube, too, when no one sees her. But when the test results come back, they are a surprise. Birdy is seemingly not related to Nora and Ben's parents. But if she is adopted, how could that have happened without the children knowing?"--

After their father's research experiment at the British Museum unleashes the Egyptian god Set, Carter and Sadie Kane embark on a dangerous journey across the globe--a quest which brings them ever closer to the truth about their family, and their links to a secret order that has existed since the time of the pharaohs.

A clue takes Amy and Dan Cahill to Egypt, where they investigate the origins of the rivalry between the Tomas and Ekaterina branches of their family and try to figure out if they can trust a message from their dead grandmother Grace.