 On 8 March 1935 he was placed in preventive detention, indicted as the "intellectual author" of a murder in Bonn.Despite the fact that the case was closed, Bästlein was sent to the concentration camp in Esterwegen and in 1936, to Sachsenhausen, where he met Robert Abshagen, Franz Jacob, Julius Leber, Harry Naujoks, Wilhelm Guddorf and Martin Weise.While at Sachsenhausen, Bästlein helped write the "Sachsenhausen Song", which was at the demand of the SS guards, who would use music to torment and mock the prisoners, making them sing while involved in hard labor or when they were exhausted.