It’s not easy being a mutant. Sure, some can manipulate metal with the twitch of a finger, and others can pop claws from their knuckles without breaking a sweat. But those strengths have become weaknesses, as far as mutantkind’s ongoing survival goes — weaknesses that, ironically enough, have led to the strongest X-Men film yet.

X-Men: Days of Future Past, the first X-Men film directed by Bryan Singer since 2002’s , marries two eras of mutantkind for the single most massive movie in Fox’s storied superhero franchise. It features no less than a dozen main characters, and many more minor mutants — and somehow, it works. The size and scope isn’t daunting. Indeed, the film’s gargantuan cast and decades-spanning story helps to make it such an epic success.

X-Men: Days of Future Past is The Avengers of the X-Men films, the biggest and best of the bunch.

Mutants face a virtually hopeless future, with genocide all but inevitable. But there are still X-Men in the world, operating as underground rebels. In China, the remnants of the X-Men gather together for one last shot at eradicating the Sentinel threat. The plan involves sending the indestructible Logan (Hugh Jackman) back through time to the 1970s to enlist a borderline drug-addicted Charles Xavier (James McAvoy) and a murderous Magneto (Michael Fassbender) into helping him stop the shape-shifting vigilante Mystique (Jennifer Lawrence) from killing Sentinel inventor Bolivar Trask (Peter Dinklage), an assassination that will inadvertently trigger the events that make the future so bleak for all mutantkind.

Whew. That’s a mouthful.

It’s a complicated plot, but it works, thanks almost entirely to the fact that the two different eras of mutants are already well established. Singer’s two X-Men films provide enough character development for folks like Bobby Drake and Colossus that when they’re smashed and shattered by Sentinels, it matters. (Not much of a spoiler, as you’ll learn when you see the film.) Matthew Vaughn’s , meanwhile, presented new takes on Xavier, Magneto and Mystique that totally worked thanks to sharp writing and even better performances. These veteran mutants are the beating heart of , the reason why it matters.

Rather than focusing on a ton of new mutants, leans on what already works. McAvoy, Fassbender, and Lawrence are right at the heart of the tale, operating as the movers and shakers of the Sentinel menace, wittingly or otherwise. Jackman, of course, gets in on the action as Wolverine, the poster-boy of the X-Men films, for better or worse. Here, however, he’s less of a leading man than ever, blending into the ensemble with ease. Really, he almost fills out the Xavier-modeled mentor role, while Chuck himself is the struggling young mutant with Wolverine-like rage.

Days of Future Past feels like a follow-up to two movies that don’t exist: a sequel to First Class and sequel to The Last Stand.

There are new mutants in the mix, of course, like the teleporting Blink (Bingbing Fan) and the fiery Sunspot (Adan Canto), but they pale in comparison to the veterans. However, there is one true highlight among the newbies: Evan Peters as the impossibly fast Quicksilver. Design issues aside (Peters could have used some more time in hair and wardrobe), Quicksilver is at the heart of one of the most entertaining scenes in the entire X-Men franchise, let alone in . You’ll know it when you see it.

Some will complain that doesn’t fully address continuity problems established in previous X-Men films. There’s no explanation for how Xavier is still alive after , nor is there any explanation for how Wolverine got his adamantium claws back after . But that’s part of the design of the film. In a way, , repeatedly described by Singer as “an inbetweequel,” feels like a follow-up to two movies that don’t exist: a proper sequel to , and a proper sequel to .

Rather than explaining how Xavier came back to life, rather than showing us how heroes like Banshee met their maker, yadda-yaddas its way through the details and gets to the meat of the matter: Sentinels eradicating mutants, and mutants fighting for their future. Who needs to know how Xavier returned from the grave when there are so many other pressing concerns?

With Days of Future Past, the X-Men franchise manages to reset some of its most glaring continuity issues, while also providing closure to the story Singer started with 2000’s X-Men. It’s emotional and action-packed, brimming with familiar heroes and villains, and fan-service for the deepest-cut X-Men lovers. It’s The Avengers of the X-Men films, the biggest and best of the bunch. It’s tempting to call Days of Future Past a surprise success, but in reality, it’s the third great X-Men film in a row. Between First Class, The Wolverine and now Days of Future Past, the X-Men franchise is on a roll. In a perfect world, all of Marvel’s characters would share the same roof — but as long as Fox can keep churning out this level of X-Men excellence, mutantkind is in good hands.

(Media © Twentieth Century Fox Film)