I n March 1965, the festering corpse of 64-year-old Herberts Cukurs was discovered stuffed into a trunk in a seaside bungalow in Montevideo, Uruguay. During the 1930s, Cukurs’ exploits as a dashing aviator had made him one of the most celebrated men in Latvia. Under the Nazi occupation, he found a new calling as a prominent member of the Arajs Kommando, the SS-affiliated killing unit responsible for the burning of the Riga ghetto and the massacre of around 25,000 Jews in Rumbula forest, among other barbarities. Cukurs was contentedly operating a pedal-boat business in Brazil when allegations of his crimes...