On March 11, 2011, a magnitude 9.0 earthquake tears open the seafloor off Japan's Tohoku coast, the largest quake ever recorded in the country, and NOVA reconstructs what happened in the minutes and months after. Seismologists and engineers walk through the physics of the rupture, explaining why the tremor triggered a tsunami with waves reaching roughly 130 feet, tall enough to lift ships onto rooftops and carry entire trains off their tracks. Footage shows the wave crossing seawalls built to hold back much smaller surges, and the film follows the failure to the Fukushima Daiichi nuclear plant, where flooding knocked out backup cooling systems and set off meltdowns and hydrogen explosions. Scientists examine why the plant's defenses were sized for a smaller disaster and what the meltdown reveals about the risks built into coastal nuclear design generally. Nearly 16,000 people died in the disaster, and the film treats the earthquake, the tsunami, and the nuclear failure as one linked chain of engineering and geological miscalculation rather than three separate accidents.