Despite Hiroshima and Nagasaki nobody knows what present-day nuclear explosions will do. And if you know, then by god you've got a massive advantage.' In 1956 a major nuclear explosion shook the southern Urals, killing hundreds, possibly thousands of Russian citizens and devestating an enormous industrial area. It could have been an accident. But was it? One man holds the final piece to a jigsaw of terrifying proportions.