Tonight on NOVA, take a look into the Nuclear Meltdown Disaster that has forever changed Japan. Four years ago, a devastating earthquake and tsunami triggered a disastrous meltdown at the Fukushima Daiichi nuclear power plant. But at the same time, just seven miles away, the heroic efforts of plant operators under the leadership of Naohiro Masuda saved a second plant, Fukushima Daini. Now Masuda faces the daunting challenge of cleaning up Daiichi, where a witches’ brew of radioactive groundwater leaks into the Pacific every day and three melted cores remain steaming hot and lethally unapproachable. With unprecedented access, NOVA reveals the little-known story of how Masuda and his team averted disaster at Daini and how workers are struggling to clean up the mess at Daiichi.