On Aug. 10, 1939, an enterprising art dealer named Justin K. Thannhauser and an eager collector, Movie Actor Edward G. Robinson, left Paris together, along with their wives, for an art-seeing holiday in Switzerland. Their main goal was an exhibition on loan from the Prado. They saw the Spanish paintings, but the Thannhausers never returned to France. World War II began, and as German-born Jews, they took sanctuary in Switzerland until they could come to New York.
One Stroke. For Thannhauser, opening a gallery in Manhattan was a third start for the family business. His father, Heinrich, had given the...