Active participation in quasi-political associations during the Weimar years evidently placed Margarete Gröwel on a list of potential government targets. The failed assassination attempt against Hitler was followed by a mass-roundup of people identified as anti-Nazis. The overwhelming majority of those arrested in what came to be known as "Aktion Gitter" had been active as members or supporters of the Communist or Social Democratic Party during the Weimar years. A handful had not. There is no indication in the sources that Gröwel was ever a Communist or a Socialist (or a Nazi), but during August 1944 she was one of approximately five thousand people arrested. She was taken to the concentration camp at on the north side of the city centre. However, she was released on 29 August 1944.