It's 1937, and eighteen-year-old Katya is working as a servant girl on the Trakehner horse breeding estate in East Prussia where she is caught up in the Nazi spirit of the time. One hot June day, Katya and her Jewish friend Minna Epstein travel to Rauschen, a spa town on the Baltic, to search for a perfect piece of amber. Helmut and David, the estate owner's two sons, accompany them and things go from peaceful and predictable to dramatic and unsettling. By summer's end, Minna has to leave for Vienna, ostensibly, to study acting. The new girl who replaces her, Gretchen, is an avid Nazi supporter. She and Helmut, an aspiring SS recruit, soon become a couple. Meanwhile, David and Katya enjoy riding in the East Prussian countryside. One evening, David, the sensitive son who will have nothing to do with Nazism, has an epileptic seizure. According to the 1935 Nuremberg Race Laws, he must be sterilized. As Katya and David struggle to salvage their relationship, Minna writes and shares how under the guise of amber hunting, Helmut seduced her and left her holding a piece of amber containing a doomed life. Breeding Trakehner horses might be an exact science, but breeding perfect Aryans is much more complicated.