As the Nazis swallowed Europe, two scientists fought back with the only weapon they had: chemistry.

When the Third Reich took control of Germany, Danish physicist Niels Bohr (pictured) transformed into something like Oskar Schindler in a lab coat. From his Institute for Theoretical Physics in Copenhagen, the Nobel laureate aided and protected Jewish scientists, a series of good deeds that landed Bohr and his Hungarian lab-mate George de Hevesy in hot water in 1940.

The Nazis had attempted to lock down Germany’s gold supply by making exportation of the metal a state crime. During the 1930s, two German physicists, the Jewish James Franck and the outspoken Hitler critic Max von Laue, smuggled their Nobel medals to Bohr’s lab for safekeeping. The lab made a perfect hiding spot until the Nazis rolled into Copenhagen in April 1940. Bohr was suddenly in a very tight spot. His reputation as a Jewish sympathizer guaranteed he would be interrogated, and the names engraved on the medals would mean death for the physicists who had trusted him.

Racing against the clock, de Hevesy saved the day by dissolving the bulky gold medals in aqua regia, a mixture of hydrochloric and nitric acids. When the German soldiers pounded on the lab’s door, all that remained of the medals was an inconspicuous bottle of reddish liquid. The Nazis, no chemistry whizzes, left empty-handed, and the dissolved Nobels sat on a shelf until the end of the war.

Once the Nazis had been defeated, de Hevesy retrieved the bottle and reversed the chemical process to separate the gold from the acid. The Nobel committee recast the medals and returned them to von Laue and Franck, proving you don’t have to leave the lab to do something gutsy.

This story originally appeared in mental_floss magazine. Now go download our iPad app! Or get a free issue of mental_floss magazine via mail.