Gerhart and Erna Fleck lived in Berlin-Mitte. To evade an imminent threat of deportation, the Jewish couple went underground on February 3, 1943. They hid on the small Reiswerder island in Lake Tegel, by passing themselves off as non-Jewish and obtaining an allotment garden. In August 1944 they took 18-year-old Gerda Lesser into their house there, since she was no longer safe in her previous hiding place with Margarete and Wilhelm Daene.
On August 23, 1944, the Flecks rowed a boat to Tegel. On entering a restaurant there, they were arrested by the Gestapo. On Reiswerder, Gerda Lesser and two others were then arrested and taken to the Schulstraße assembly camp. On September 5, 1944, Erna and Gerhart Fleck and Gerda Lesser were deported to Theresienstadt, where the couple were separated. On September 28, 1944, Gerhart Fleck was taken to Auschwitz. Erna Fleck survived; her husband is thought to have died of typhus in Gleiwitz concentration camp, a sub-camp of Auschwitz, at the end of 1944.