Double helix (National Geographic Kids)

The mystery deepens and the action intensifies for 12-year-old Cruz Coronado and friends in the exciting third book in the Explorer Academy series. The adventure continues for Cruz, Emmett, Sailor, and Bryndis as they continue their studies at sea and travel to exotic locations around the world.

A mysterious person alerts Cruz to impending danger while he and a few trusted pals explore ancient ruins in Petra, Jordan, and search for another piece of the puzzle his mother left behind. Worst of all, now his father has gone missing, which prompts Aunt Marisol, his #1 protector, to leave the ship in search of him.

Who is the new professor who takes her place$47 How does the new technology he introduces help or hurt Cruz's quest$48 Why is Nebula determined to stop Cruz before he turns 13$49 The clock is ticking as his first teen birthday draws near...

a milestone that will change his life forever, one way or another.