• “X-Men: First Class,” Directed by Matthew Vaughn, 20th Century Fox, 132 minutes, released June 3.

History students often wonder what forces brought the world so close to all-out nuclear war during the Cuban missile crisis. “X-Men: First Class,” Matthew Vaughn’s new prequel to the blockbuster X-Men franchise, offers an unusual answer, placing mutant superheroes at the center of world events.

This slick origin story reveals the beginning of Professor X’s School for young mutants and the deep philosophical differences between him and his former friend Magneto, head of the nefarious Brotherhood.

The story opens with painful scenes from the childhood of Eric Lehnsherr (Michael Fassbender), a Jewish child torn from his parents during the Holocaust. A power-hungry Nazi colonel named Schmidt (Kevin Bacon), himself a mutant, will stop at nothing to force the boy into revealing his surprising magnetic powers. Tortured, crushed, and emotionally destroyed, Eric survives the war, but swears eternal vengeance on his family’s killers.

Charles Xavier’s privileged upbringing charts a very different path, as the telepathic youth (played by James McAvoy) grows up in the lap of luxury in Westchester, N.Y. His generous nature leads him to offer a home to an orphan shapeshifter named Raven (Jennifer Lawrence), and they grow up as brother and sister, with no one in their privileged circles aware of their special talents.

When CIA agent Moira MacTaggert (Rose Byrne) witnesses three mutants blackmailing a highly placed U.S. military officer in the shady Hellfire club, no one in the sexist CIA bureaucracy will believe her. She enlists the help of Dr. Xavier, now researching genetic mutations at Oxford, with his sister Raven never very far from his side.

Charles agrees to return to the States to convince the CIA, but when he and Raven reveal themselves as mutants, they’re immediately taken into custody. Their captor, however, long has been interested in mutants, and with the help of Dr. Hank McCoy, a fellow mutant, they develop the first version of Cerebro, an amplifying antenna array that allows Charles to reach out and identify more mutants scattered through the population, eventually massing a promising young team to work with the CIA.

On their first mission against the shadowy Shaw, Charles saves the life of the angst-ridden Eric, who was seeking revenge independently against the man who ruined his life. While his magnetic powers are strong, Eric introduces a note of doubt into the team, with his distrust of authority and anger issues, convinced the world will turn against mutants the way Germany turned against the Jews. The two form a close friendship despite their philosophical differences, and come to advise the younger mutants as they explore their powers and choose new names and identities for themselves.

With Charles and Eric on a mission deep inside Soviet Russia, Shaw strikes the CIA facility where the young mutants are housed. After killing most of the normal humans in the facility, Shaw invites the young mutants to join his revolutionary cell, bent on remaking the world to advance mutant interests. One of the mutants is killed cruelly, and another decides to join Shaw’s cabal.

Over the following weeks, Shaw’s master plan is revealed gradually — the renegade precipitates the Cuban Missile Crisis and places the world on the brink of nuclear war. The young mutants must prepare themselves for a mission that will stretch them to the breaking point, and sweep away their precious privacy, placing them irretrievably in the public eye. Only time will tell whether Xavier’s rosy vision of symbiotic mutant-human relations or Eric’s gloomy predictions of discrimination and extermination will be closer to the truth.

This prequel breaks all the rules in setting up characters’ back stories. While not a total reboot, as it maintains the visual continuity of the original trilogy, the writers recast the back stories of Beast, Havoc, and Mystique, usually making them far younger so they can play a realistic part in this fledgling group of X-Men.

Purists will be outraged, but the story is consistent and relatively satisfying. The historical context is rewritten, with the vast machinations of U.S. missiles being placed in Turkey, and the subsequent Cuban Missile Crisis shown to be the work of Dr. Shaw’s apocalyptic cell of mutants. While the plot is littered with historical references, most of it feels tacked-on.

Parents may want to be careful about this film. Even by the relaxed standards of superhero movies, this flick crosses the line at several points. Moira strips down in one scene to “use some equipment the CIA didn’t give me.” Emma Frost often is seen half-clothed, and uses her telepathic powers of (sexual) suggestion to deceive and control.

The film holds together well. While partially undermined by the dark events that lead to their eventual schism, Charles’ friendship and hope balance Eric’s emotional scars and angst. The generally upbeat storyline is confined by the requirements of a prequel, however, and ends on a hard note as the mutant community remains split, separated by their warring philosophies.

The film touches on a number of important themes, from the value of individual identity to the horror of situational ethics and the ruinous danger posed by a society that elevates itself above individuality. Ultimately, however, it is no more or less than a slick summer action flick that is a worthy addition to the X-Men franchise.