The Oversteegen sisters and friend Hannie Schaft worked to sabotage the Nazi military presence in the Netherlands. They used dynamite to disable bridges and railroad tracks. Additionally, they aided Jewish children by smuggling them out of the country or helping them escape concentration camps.
The Oversteegens and Schaft also lured German soldiers to the woods under the pretense of a romantic overture and then killed them. Freddie would approach the soldiers in taverns and bars and ask them to "go for a stroll" in the forest.