After intriguing side stories like X-Men: First Class and The Wolverine, the blockbuster X-Men franchise is getting back to basics with next year's X-Men: Days of Future Past — and the threat the X-Men are facing is so enormous that they're teaming up with the series' villains to take it on. "You need me," says Magneto (Ian McKellan) to Professor X (Patrick Stewart) in the film's trailer, which hit the internet Tuesday morning. "Side by side, to end this war before it ever begins."

But those are just two of the many, many mutants who appear in the blockbuster film. Days of Future Past is the event that fans have been anticipating since the release of X-Men: First Class, which served as a prequel to the original X-Men trilogy. The film bridges the decades that separate the two movies with a time travel plot that sees the older X-Men confronting their younger selves — many of whom seem to have fallen on hard times. "I don't want your suffering! I don't want your future!" screams young Professor X (James McAvoy) at his older self (Patrick Stewart). "Please. We need you to hope again," replies the older man.

It's all a little dizzying, though it's undeniably thrilling to see so many great actors from the franchise's increasingly convoluted history in one place. Days of Future Past's story is an acknowledged classic in comic book circles, with some fans arguing that it's the best story X-Men ever told — but will mainstream film audiences embrace the mind-bending storyline? We'll find out when X-Men: Days of Future Past kicks off the summer blockbuster season next May.