While acting as a Swedish diplomat in Hungary, he invented and issued Swedish-looking passports for these people, called Shutzpass, and set up safe houses for them.
When the Soviet army took the east part of Budapest in January 1945, Wallenburg was taken to Moscow as prisoner. The details of what happened after that are unclear, and his fate is still a mystery.
"The rest of the embassy came back in April, so we waited for his [return], too," says Lagergren, who criticizes Sweden for not doing enough in handling his case.
"So, started this very sad period when the Swedes did not act as forcefully as one could have expected to someone who had done such enormous work to save people," says Lagergren.
In 2000, Lagergren won a Wallenberg medal from the University of Michigan – putting her in the company of Desmond Tutu, Aung San Suu Kyi, and others – for her tireless work to learn the full story of her brother's fate and to educate children about his humanitarian accomplishments.