For those of you who don't know much about the 1986 comic, here's a tidbit from our friends at wikipedia:
"Watchmen is set in an alternate reality which closely mirrors the contemporary world of the 1980s. The primary point of divergence is the presence of superheroes. Their existence in this iteration of America is shown to have dramatically affected and altered the outcomes of real-world events such as the Vietnam War and the presidency of Richard Nixon. In keeping with the realism of the series, although the costumed crime fighters of Watchmen are commonly called 'superheroes', the only character in the principal cast who possesses obvious superhuman powers is Doctor Manhattan. The existence of Doctor Manhattan has given the U.S. a strategic advantage over the Soviet Union, which has increased tensions between the nations. Additionally, superheroes have become unpopular among the public, which has led to the passage of legislation in 1977 to outlaw them."
"The story focuses on the personal development and struggles of the protagonists as an investigation into the murder of a government sponsored super-hero pulls them out of retirement and eventually leads them to confront a plot by one of their own to stave off nuclear war by killing millions of innocent people."