Jon Hamm, Vincent Kartheiser. Photo: AMC

We head into Mad Men’s fifth season knowing nothing about it. The on-air promos recycle moments from past seasons, and the teaser art has been cryptic even by this show’s standards: an opening-credits-styled image of a falling man that could be hawking any season, and a photo of hero Don Draper staring at two mannequins — a clothed male and a naked female* — through a dress-shop window. Matthew Weiner, who banned advance screeners after a New York Times review revealed innocuous details from the season-four premiere, has dropped a cone of silence over the production. We have no idea if Don went through with plans to wed his young secretary, Megan; if Joan had Roger’s baby; or if the new agency is still in business. We don’t even know the year in which this season takes place, which at least would prepare us for the wingspan of Roger’s lapels.

On first glance, the black-ops secrecy seems insane. This isn’t a plot-twisty series like Breaking Bad or Homeland; it’s a low-key drama consisting largely of men and women in vintage clothes bantering on the same eight or nine sets. And yet the cloak-and-dagger shtick is of a piece with what’s onscreen. It’s a rare show that can vanish for seventeen months, make a tight-lipped and rather self-satisfied return, and presume we’ll give it a prodigal son’s welcome and be right. Mad Men has earned that level of blind trust because it’s serenely sure of what it’s doing.

Despite the umpteen-zillion forest-for-the-trees “think pieces” grousing that Mad Men doesn’t “get” sixties-era advertising, feminism, racism, chauvinism, alcoholism, culture, fashion, etc., the show’s appeal has little to do with period embellishment. The hits Boardwalk Empire and Downton Abbey, the underappreciated The Borgias, the promising but still unsteady Pan Am and Hell on Wheels, and the dead-on-arrival The Playboy Club — to name but a few lavish period dramas that followed in Mad Men’s wake — were each wedded to a specific era and would have been unthinkable without it. Not so Mad Men. Weiner’s show is set in the American Northeast in the sixties, a time of immense social, sexual, and political upheaval, but it isn’t solely, or even mostly, about its time and place. The show’s main draw is behavior, observed with such exactness that one can imagine the show’s being transposed to the forties or eighties, with different clothes, slang, and inebriants, and still delivering the same basic satisfactions.

It’s not hard to imagine Don Draper circa 1942 selling “Loose Lips Sink Ships” to the War Department, Joan snorting coke off a glass tabletop at Studio 54 in the seventies, or Weiner staging an equivalent of the JFK episode about 9/11. A period transplant would change the historical details, pop-culture references, and mores, but not the characters, tone, or themes. Mad Men would still be Mad Men because the show isn’t about history. It’s about mystery — specifically the mystery of personality. Weiner practices sawdust-and-footlights dramaturgy. Scenes go on longer than TV’s norm and let significant action play out in wide shots that turn the edges of the screen into a proscenium. For all its snappy dialogue, the show’s most piercing moments are silent: Don, AWOL from his daughter’s birthday party, parked at a railroad crossing while a train rumbles past; ex-lovers Peggy and Pete regarding each other through a glass partition; Don and Peggy curled on Don’s office couch like shipwreck survivors on a raft.

This is not Deadwood, with its grubby optimism about society’s and the individual’s potential for change. It’s not The Wire or Treme, with their humanistic empathy for citizens let down by governments and institutions. It’s not the black-comically pessimistic Seinfeld or Curb Your Enthusiasm or The Sopranos, on which characters crow about improving themselves, then revert to type with a vengeance. It’s more elusive, archetypal, and intimate. Mad Men’s characters are more true to life than any others on TV because they’re so random, inscrutable, and mysterious, and because there’s no propulsive generic master narrative (the building of a gangster coalition, the completion of a stretch of railroad track, the creation of an innovative drug cartel) on which to string their decisions, revelations, and misfortunes. People do things and have things done to them while history rolls invisibly forward. Some of the show’s plot twists are out-of-nowhere melodramatic, and Weiner has a flair for turning subtext into text (while every major character commits deceptions and struggles with identity issues, Don is literally an impostor). But calling Mad Men a high-toned soap opera isn’t accurate, because when soap characters announce their motivations and analyze their impulses, we’re usually supposed to take whatever they say at face value. On Mad Men, explanatory speeches and dream sequences tend to muddy motivation rather than clarify it.

Why did Don suddenly propose to his young secretary, Megan, following a trip to California with his kids? Don’s previous lover, the professional woman Faye, was roughly his age and intellectual equal and shared some of his pathologies; did that make her a threat? Is Megan appealing because she’s a blank slate who treats Don as a blank slate too? Maybe. Or maybe Don proposed because it seemed like a good idea at the time. Why did Joan impulsively have sex with her ex-boyfriend Roger while her husband was in Vietnam, after she’d established that the relationship was dead and should stay dead? Was it just residual heat from the near-death experience of being mugged, or was a deeper wish being expressed? We don’t know and probably never will. Why is Peggy attracted to scheming man-boys like Pete and Duck, and what’s the essence of her bond with Don? She treats him as, alternately, a father figure, a brother, and an overgrown child. What do they mean to each other? Mad Men won’t tell us. It’s anti-theory. It’s about human behavior observed in the moment. It doesn’t explain. It observes. It’s not about the period, it’s about the question mark.

*An earlier version of this piece misidentified the gender of one of the mannequins in the ad for Mad Men’s fifth season