The tunnel is in Lithuania's Ponar forest. The Nazis killed about 100,000 people in the forest and dumped the bodies in pits in the ground. The victims included 70,000 Jewish people.
Toward the end of WWII, the Nazis tried to erase the evidence of their mass killings. Jewish and Soviet prisoners were sent to Ponar. They were kept in chains. They were forced to dig up the mass graves.
The prisoners were nicknamed the Burning Brigade. They had to collect the buried bodies and burn them. They lived in fear that they would be killed after their work was done.
According to accounts, Isaac Dogim was a member of the Burning Brigade. One day, he found the bodies of his wife and family in the pits. He knew his wife from a necklace he had given her for their wedding.
Dogim put together a plan for escape.