Student years at Niels Bohr Institutet in the late 1920s; influence of Lev Landau and study of Hans Bethe's thesis on scattering of fast neutrons and to a lectureship at the Institute in 1929. Bohr's switch to nuclear physics in mid-1930s; the informal conferences at the Institute. Travels to Rome and to Cambridge, 1935-1936, reporting to Bohr on Fermi's work on resonances. Travel to U.S.S.R. in September and October of 1936; gives talk on Bohr's paper on neutron captive and nuclear constitution; collaboration with Leipunski on k-electrons; comments on life at Physical Technical Institute, arrests of Landau, Houtermans, and Weissberg; tension in Russia. Continued work on capture of k-electrons and meson theory work with Lǒn Rosenfeld. Teaching; students demand course in quantum mechanics. George de Hevesy's association with the Bohr Institutet (biology); popular science writing and publication procedures. German occupation of Denmark, 1940-1945, and the Institutet, December 1943 to February 1944; comments on the political and social situation prior to World War II. Werner Heisenberg as head of a German committee investigating the Institutet.