On October 2, 1938, Lise Meitner arrived in Stockholm after nearly four months in exile. She had fled Germany on July 13, crossing the Dutch border without a visa, a year after Austria had been annexed and her Austrian citizenship had been replaced with German citizenship — which stripped her of legal protections as a Jew. She was sixty years old. She had left behind thirty years of work at the Kaiser Wilhelm Institute, her laboratory equipment, most of her papers, and whatever professional standing the Nazi government had left her.

Meitner was born in 1878 in Vienna. She earned a doctorate in physics from the University of Vienna in 1906 — the second woman ever to do so — and joined Otto Hahn at the Kaiser Wilhelm Institute in Berlin in 1907. For thirty years they collaborated on radioactivity research. She discovered the element protactinium with Hahn. She built the Institute's physics section from nothing. For years she was permitted to work only in the basement because the Institute's director did not believe women should be in the building.

In December 1938, Hahn sent her a letter from Berlin describing results from experiments they had designed together. He had bombarded uranium with neutrons and found barium in the products — a finding he could not explain. Meitner and her nephew Otto Frisch, working through the physics over a walk in the snow in Sweden, provided the explanation: the uranium nucleus had split. They named the process nuclear fission. They published the theoretical explanation in January 1939.

Hahn received the Nobel Prize in Chemistry in 1944 for the discovery of fission. Meitner was not included.