We do not know their names, their faces, their families or their personal stories. Nobody really does. They are strangers, in a faraway land, doing the unthinkable. In Japan they have a name: The Fukushima 50. A coterie of nuclear plant employees - some reports indicate 50, others suggest four working rotations of 50 - who stayed behind while 700 of their co-workers were evacuated from the stricken Fukushima-Daiichi facility on the Japanese coast.

Five have been killed. Two are missing. Twenty-one have been injured in a struggle where, in the words of Japan's Prime Minister Naoto Kan, "retreat is unthinkable." The men understand the stakes. They know there is no turning back. One worker told a departing colleague he was prepared to die - that it was his job. Another informed his wife he wouldn't be coming home anytime soon.

And so they battle on, a weary bunch of managers, operators, technicians, soldiers, firemen, amid rumours, worst-case scenarios and startling television footage.

They are mid- and low-level employees. They are men with no names, cast into extraordinary circumstances, battling fires, explosions, the threat of explosion and the invisible menace: dangerously high levels of radiation no protective suit can deflect, and one that threatens to seep into the atmosphere if they fail.