Arcady and Boris Strugatsky.Prisoners of Power Early in these pages, when young Maxim dips his hand into a river on the alien planet on which he has just been marooned, and withdraws it hastily because the water is radioactive, the knowledgeable science fiction reader is likely to say, "Come on, now, fellows -- how could he know? Or, if it were so devastatingly, dangerously radioactive that he could determine it without instruments, how could he notnot know before he stuck iris silly hand i