The Charlemagne Pursuit Cotton Malone #4 by Steve Berry

 Cotton is getting busy again. This time he is on the hunt for the mystery that surrounds the fate of his own father. His father died when he was ten-years-old during a top secret mission on an experimental submarine. Cotton has many unsolved issues growing up without a father. This is personal. But he has a mysterious German family, assassins and double-crossing people from his own government that are trying to stop him from finding the truth.

Fast-paced twists and suspense are hidden in an ancient past will excite any thriller fan.