Lev Termen is imprisoned on a ship steaming its way from New York City to the Soviet Union. He is writing a letter to his "one true love," Clara Rockmore, the finest theremin player in the world. From there we learn Termen's story: his early days as a scientist in Leningrad, and the acclaim he received as the inventor of the theremin, eventually coming to New York. But it isn't long until he has fallen in with Russian spooks.