Bily Crudup plays the radiantly blue Dr. Manhattan in "Watchmen," directed by Zack Snyder.

LOS ANGELES — Fans should plan to savor every visual morsel when "Watchmen" swoops into movie theaters because the subversive superheroes of the landmark comic book series may never return to the big screen.

"There's no way I would be involved in a sequel or prequel," said director Zack Snyder, who turned the graphic novel "300" into a 2007 blockbuster.

"Will they make one? I have no idea how you would. The work is the work. This movie is about ideas. Anything else you would do, if you did a sequel to it, misses the point entirely of what 'Watchmen' is," he said.

It's unclear whether Warner Bros. would ever take a cue from Dr. Manhattan, the blue-hued superbeing played by Billy Crudup who smoothly proclaims in the comic and the movie that "nothing ever ends." Jeff Robinov, president of Warner Bros. production, declined to be interviewed for this story.

"Contractually, we are obligated," Crudup said. "I will do it. I just don't know what it is we would do."

Unlike superheroes with superhistories like "Batman" or "Spider-Man," decades worth of "Watchmen" source material doesn't exist.

In the 1980s, illustrator Dave Gibbons and writer Alan Moore (who has said he doesn't want to be associated with a "Watchmen" film) crafted only 12 chapters of the comic book-turned-graphic novel.

The nearly three-hour R-rated movie is faithful to the original novel, leaving almost nothing on the cutting room floor except "Tales of the Black Freighter," a comic-within-the-comic woven throughout "Watchmen." It will be released March 24 on DVD as an animated short film along with "Under the Hood," the tell-all memoir from "Watchmen."

Beyond that, Snyder can't envision any cinematic additions to the mythos.

"What? In the next movie, they redeem themselves?" Snyder said. "To continue is to either rehash the same idea again or you're going to try to fix the characters, which goes against everything the book stands for, or you could pick up new characters — or I don't know what. To me, philosophically, it just doesn't make sense."