"One thing is clear. These posters are trouble." That's the message artist Benny Nemer gave in an audio letter to Jane Becker Nelson, director and curator of the Flaten Art Museum at St. Olaf College.

The story of Mildred Harnack, a woman from Milwaukee who led resistance to Adolf Hitler's regime from her Berlin apartment, is personal for biographer Rebecca Donner. Harnack, executed by the Nazis in ...