The Watchmen is a comic book written by the English comic master Alan Moore and illustrated by the artist Dave Gibbons.
It's a kind of fiction book centered on superheroes, but it debunks most of the myths and patterns that we were used to find in classical comics starring Superman or Batman.

The leading thread of the Watchmen is a simple catchphrase that emerges here and then in the story: “who watches the watchmen?”.
The plot begins in 1985 with the murder of the Comedian and with a focus on a weird character whose face is covered with a white piece of sheet representing a Rorschach drawing.
Both used to belong to a league of superheroes that used to work under the cover name of “the Watchmen”.

Who … is the question voiced by the population of New York City. In a sort of panic and suspicion surge ( 1985 is a bad time for America), people asked the police to get rid of superheroes.
The only one remaining under contract with the government is Doctor Manhattan a blue sort-of-giant man who has nuclear abilities.
He's actually the only one possessing superpowers.

After the death of the comedian, the watchmen get back to work, not to stop crimes, but to find out who wants to frame them in this gloomy world; sort of “what if?” present in which Nixon is the president instead of Reagan and in which the USA won the Vietnam war thanks to Doc Manhattan.

It's different from other superheros stories, as it relates how these once-upon-a-time heroes with seldom powers get old and devastated by problems ( alcoholism, rapes, nihilism, violence....).
The story doesn't take place in a futurist setting and doesn't brag about being a science-fiction piece of work.
Moore had already written the plot of the gloomiest Batman series...

A movie adaptation was first given a try by Terry Gilliam, but it was finally released in 2009 and directed by zack snyder.