Daddy by Loup Durand was a bestseller in France but, amazingly, never a huge hit in the U.S.  

Thomas, an 11-year-old genius, is being chased by Nazis, after they discover the boy’s grandfather has entrusted him with information about Jewish fortunes held in Swiss bank accounts.

American millionaire David Quartermain, the father Thomas has never known, is summoned by the child’s mother when she realizes her life is in danger. Not only an incredibly tense cat-and-mouse chase novel, this is also the story of how father and son learn to trust and love each other.

Intricately plotted, there are iconic characters (a sociopathic Nazi, a mysterious sniper/bodyguard and wealthy playboy turned patriot), mysteries, secrets, and  the always-fascinating setting of World War II Europe. A great and satisfying page-turner.