Kenji Mizoguchi's masterpiece opens in 11th-century Japan with an aristocratic woman Tamaki traveling through the woods with her daughter Anju, son Zushio, and maid. Through flashbacks, we learn that her husband, Taira no Masauji, was a local governor who was exiled because of his honesty and integrity.
Before he leaves, he gives his son an amulet of Kannon, the goddess of mercy, and tells him, Without mercy, man is like a beast. Men are created equal, everyone is entitled to happiness.
On their journey to reunite with their husband/father, they are ambushed by kidnappers, who sell the mother as a prostitute and the two children as slaves to the corrupt Sansho (Eitaro Shindo). As adults, Zushio (Yoshiaki Hanayagi) and his sister Anju (Kyoko Kagawa) continue to toil as servants.
Anju learns that her mother has become a courtesan on remote Sado-island. Though Zushio became Sansho's most trusted and most brutal aide; he manages to escape at Anju's behest. He finds sanctuary at a local monastery while Anju, looking to avoid the inevitably violent retribution, drowns herself in a lake.
Seeking justice, Zushio petitions the Prime Minister, a desperate act that usually results in imprisonment or death. Yet his pleas prove more successful than he ever dreamed. When he finally has the power to thwart evil Sansho and reunify his family, he learns that he is tragically too late.