"Sigrid MacRae never knew her father, until a trove of letters revealed not only him, but also the singular story of her parents' intercontinental love affair. While visiting Paris in 1927, her American mother, Aimée, raised in a wealthy Connecticut family, falls in love with a charming, sophisticated Baltic German baron, a penniless exile of the Russian revolution. They marry. But the harsh reality of post-World War I Germany is inescapable: a bleak...