Hanna's War is the true story of Hanna Senesh, a Hungarian-Jewish WW2 resistance fighter, who would become Israel's "Joan of Arc". As a young person, she fled Nazi-occupied Hungary for Palestine, where she was recruited and trained by the British to serve as a commando. After completing her training in Britain, she parachutes into Yugoslavia with a commando team to establish escape routes across the Hungarian-Yugoslavian border for downed British pilots. Her attempts to save Hungarian Jews in Nazi-occupied Hungary, however, leads to her capture, torture and demise at the hands of the Gestapo and the Nazi-controlled Hungarian police.

Though it happened decades before, Roland Kadar is still unclear as to the circumstances that led his father Paul to drown himself in the Danube during the 1950s, and so he heads to Europe to find out for himself. His grim journey takes him to such places as Budapest, Warsaw and Prague. He even visits Tokyo. The major scenes consist of interiors inter-spliced with black-and-white footage of other European locals and old family photographs.