Andre Norton 
Sword Is Drawn 

Young Lorens van Norreys must save his family legacy from Nazi invasion in this thrilling series opener from the New York Times–bestselling author. The House of Norreys—those merchants of gems for over three hundred years—faces its greatest crisis ever: the Nazi occupation of the Netherlands. The old Jonkheer lay dying in his bed when he called his grandson to be with him in the last hours of his life, and at this time, young Lorens van Norreys is entrusted with the future of Norreys. That future lies in the legendary Flower of Orange, a priceless baroque necklace that the Nazi scavengers burn to possess. It is up to Lorens to save the necklace and the House of Norreys. With the first encounter with the Nazi invaders, Lorens faces his challenge as The Sword Is Drawn.