Half a century after he disappeared into the Soviet prison system, the fate of Raoul Wallenberg--who saved thousands of Hungarian Jews during the Holocaust--remains a mystery. Following the collapse of the Soviet Union, KGB files were opened, but the Wallenberg file had been destroyed, thereby eliminating any evidence to support the Kremlin's claim that Wallenberg died in prison in 1947. Bierman concludes that we may never know the truth. Photos.