The Serpent's Egg: A WW2 spy story

Berlin 1938. Max and Anna are in love and want to get married, but their union is against Nazi laws, as Anna is part-Jewish. A Gestapo officer agrees to authorize the marriage, but only if Max infiltrates and betrays a Marxist resistance cell, the Red Orchestra. This is not an assignment that Max can refuse. If he succeeds, Anna will get the wedding she longs for, but many brave resistance fighters will die...