World War III is over -- a nuclear holocaust begun when the Republic of Turrannia detonated a suitcase bomb in an American city, in retaliation for the assassination of their President.

Two years after the bombs, a super-scientist has developed a rudimentary time machine. There's enough power for a single window to open for a few minutes. A few of the world's remaining heroes (along with a villain or two) volunteer to go back in time and prevent the apocalypse by eliminating the superhero who assassinated the Turrannian President.

Unfortunately, that superhero is one of the Player Characters.